> If you (as a commercial ISV) target a commercial distro with long-term support, and can convince your users to use / license the same distro, you'll have a good, stable development experience. You only need to port like once every decade, when you jump major releases.

If things go well, it's even better than that: If you target ex. RHEL 8, there's a very good chance that your binaries will work on RHEL 9 and a decent shot at RHEL 10 with zero changes (though of course you should test all versions you want to work). And the same for Ubuntu 20.04/22.04/24.04/... and Debian/SUSE/whatever. Backwards incompatibilities can happen, but within a single stable distro they're not super common so the lazy ISV can probably only really port forward after more than a decade if they really want.

(Incidentally, this isn't a hypothetical: I once had the joy of working on software that targeted RHEL 5, and those binaries ran on RHEL/CentOS 7 without any problems.)