Try to Connect to ldaps (Microsoft AD) fails on Debian 10 , Foreman 1.24. The Enterprise PKI CA Certificate is sucsessfull importet.

root@XXXXXXX:/usr/local/share/ca-certificates# openssl s_client connect XXXXXXXX:3269
CONNECTED
write:errno=104
--
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 0 bytes and written 311 bytes

Here the return from WUI
Foreman::LdapException
ERF77-8135 [Foreman::LdapException]: Error while connecting to 'MLR' LDAP server at 'mlrsd01.mlr.bwl.net' during authentication ([Net::LDAP::Error]: Connection reset by peer - SSL_connect)
/usr/share/foreman/app/models/auth_sources/auth_source_ldap.rb:80:in `rescue in authenticate'
/usr/share/foreman/app/models/auth_sources/auth_source_ldap.rb:56:in `authenticate'
/usr/share/foreman/app/models/user.rb:242:in `try_to_login'
/usr/share/foreman/app/controllers/users_controller.rb:114:in `login'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/basic_implicit_render.rb:6:in `send_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/abstract_controller/base.rb:194:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/rendering.rb:30:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/abstract_controller/callbacks.rb:42:in `block in process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:109:in `block in run_callbacks'
/usr/share/foreman/app/controllers/concerns/foreman/controller/timezone.rb:10:in `set_timezone'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks'
/usr/share/foreman/app/models/concerns/foreman/thread_session.rb:32:in `clear_thread'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks'
/usr/share/foreman/app/controllers/concerns/foreman/controller/topbar_sweeper.rb:12:in `set_topbar_sweeper_controller'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks'
/usr/share/foreman/vendor/ruby/2.5.0/gems/audited-4.9.0/lib/audited/sweeper.rb:14:in `around'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks'
/usr/share/foreman/vendor/ruby/2.5.0/gems/audited-4.9.0/lib/audited/sweeper.rb:14:in `around'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:118:in `block in run_callbacks'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:136:in `run_callbacks'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/abstract_controller/callbacks.rb:41:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/rescue.rb:22:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/instrumentation.rb:34:in `block in process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/notifications.rb:168:in `block in instrument'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/notifications/instrumenter.rb:23:in `instrument'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/notifications.rb:168:in `instrument'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/instrumentation.rb:32:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal/params_wrapper.rb:256:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activerecord-5.2.1/lib/active_record/railties/controller_runtime.rb:24:in `process_action'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/abstract_controller/base.rb:134:in `process'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionview-5.2.1/lib/action_view/rendering.rb:32:in `process'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal.rb:191:in `dispatch'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_controller/metal.rb:252:in `dispatch'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:52:in `dispatch'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:34:in `serve'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:52:in `block in serve'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:35:in `each'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/journey/router.rb:35:in `serve'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/routing/route_set.rb:840:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/apipie-rails-0.5.17/lib/apipie/static_dispatcher.rb:66:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/apipie-rails-0.5.17/lib/apipie/extractor/recorder.rb:137:in `call'
/usr/share/foreman/lib/foreman/middleware/telemetry.rb:10:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/apipie-rails-0.5.17/lib/apipie/middleware/checksum_in_headers.rb:27:in `call'
/usr/share/foreman/lib/foreman/middleware/catch_json_parse_errors.rb:9:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/tempfile_reaper.rb:17:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/etag.rb:27:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/conditional_get.rb:40:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/head.rb:14:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/http/content_security_policy.rb:18:in `call'
/usr/share/foreman/lib/foreman/middleware/logging_context_session.rb:22:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/session/abstract/id.rb:277:in `context'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/session/abstract/id.rb:271:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/cookies.rb:670:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/callbacks.rb:98:in `run_callbacks'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/callbacks.rb:26:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/debug_exceptions.rb:61:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/railties-5.2.1/lib/rails/rack/logger.rb:38:in `call_app'
/usr/share/foreman/vendor/ruby/2.5.0/gems/railties-5.2.1/lib/rails/rack/logger.rb:28:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/sprockets-rails-3.2.1/lib/sprockets/rails/quiet_assets.rb:13:in `call'
/usr/share/foreman/lib/foreman/middleware/logging_context_request.rb:11:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/remote_ip.rb:81:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/request_id.rb:27:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/method_override.rb:24:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/runtime.rb:24:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/activesupport-5.2.1/lib/active_support/cache/strategy/local_cache_middleware.rb:29:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/executor.rb:14:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/actionpack-5.2.1/lib/action_dispatch/middleware/static.rb:127:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/sendfile.rb:113:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/secure_headers-6.2.0/lib/secure_headers/middleware.rb:11:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/railties-5.2.1/lib/rails/engine.rb:524:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/railties-5.2.1/lib/rails/railtie.rb:190:in `public_send'
/usr/share/foreman/vendor/ruby/2.5.0/gems/railties-5.2.1/lib/rails/railtie.rb:190:in `method_missing'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/urlmap.rb:77:in `block in call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/urlmap.rb:61:in `each'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/urlmap.rb:61:in `call'
/usr/share/foreman/vendor/ruby/2.5.0/gems/rack-2.1.1/lib/rack/handler/webrick.rb:88:in `service'
/usr/lib/ruby/2.5.0/webrick/httpserver.rb:140:in `service'
/usr/lib/ruby/2.5.0/webrick/httpserver.rb:96:in `run'
/usr/lib/ruby/2.5.0/webrick/server.rb:307:in `block in start_thread'
/usr/share/foreman/vendor/ruby/2.5.0/gems/logging-2.2.2/lib/logging/diagnostic_context.rb:474:in `block in create_with_logging_context'
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)