multiple_checkboxes calls ActiveModel::Naming on associations that could be simply "Taxonomy". This results on a 500 error 'undefined method `taxonomies' for #<Filter:0x005593624bdd18>' (or whatever other class has the problem). Simply trying to edit a filter will throw this 500 error.

https://github.com/theforeman/foreman/blob/develop/app/helpers/form_helper.rb#L49

We've always had this problem , but since #16971 removed the check for only using that method for '> 5' associations, you'd only see the error if you had at least 6 organizations or locations (unlikely). Now it became more apparent and it shows up every time.