@Bernhard

I think your PR/commit introduced issues. We are one of the lonely PXElinux (not iPXE) users out there and when using the new templates in Foreman 3.3, we get "malformed ip adress" in the Ubuntu installer.
Our subnet is set to bootmode "static", so your new "preseed_kernel_options" template is setting f.e. "netcfg/get_ipaddress=${netX/ip}" kernel options. It looks like these variables (netX/ip) are somewhat specific to iPXE and are not processed by PXElinux. So the PXElinux just passed that "variable" string through leading to the installer seeing a malformed ip address. Maybe it is redundant anyway, since the preseed template sets the same options.

I am absolutely no specialist in any of the PXEs, so i am writing here to hear your opinion first. Once confirmed, we can look for a solution.

A colleague of mine is already working on it: https://github.com/theforeman/foreman/pull/9281/files
Maybe you can help by some tests, comments and review? Would be very appreciated.