Today it’s not possible to run Foreman on CentOS 8 Stream without some additional work. At least Bug #31527: foreman-installer fails to configure Postgres on CentOS Stream 8 - Installer - Foreman is a known blocker. The short summary of that is that the Apache and PostgreSQL Puppet modules assume EL8 has a minor version but stream doesn’t.
Untested, but I think the workaround is adding the following to
I don’t expect to fix this in time for Foreman 2.4. It’s also complicated by the fact that there are no vagrant boxes nor containers which makes automated testing harder.