For Ubuntu they would only target LTS releases, most likely.

On EL it's easier, now you would just support 2 or 3 of EL7, EL8, and EL9.

As an example of something I use, Xfdtd only officially supports one version of Ubuntu and 2 versions of EL https://www.remcom.com/system-requirements#xfdtd-system-requ...

In practice, it wasn't too hard to get it running on EL9 or Fedora either...