Re the flatpak issue, what you linked is just saying that flatpak won't be a default installed program and packages provided by flatpaks won't be officially supported by Ubuntu support as of 23.03. I don't think this effects your use of Ubuntu in any way. If you want to use flatpaks, just install the program. It will still be packaged in the Ubuntu repositories. 23.04 was over a year ago. I still use flatpak without a problem on my kubuntu 24.04 system. It's just a one time thing to do sudo apt-get install flatpak
and maybe a second package for KDE's flatpak packagekit back end and it's like canonical never made that decision.
The push of snaps instead of debs is a bit more concerning because it removes the deb as an option in the official repositories. But as of right now I think only Mozilla software has this happening? If your timeline is 5-10 years though, this may be more of an issue depending on how hard canonical pushes snaps and how large their downsides remain
I compile them because I want to use them with my system wine, and not with proton. Proton does that stuff for you for steam games. This is for like CAD software that needs accelerated graphics. I could probably use like wine-ge and let GE compile it for me, but I'm not sure they include all the Nvapi/cuda stuff that's needed for CAD and not gaming. If there's an easier way to do it, I'd love to hear! Right now I'm using https://github.com/SveSop/nvidia-libs
If you're a developer that's comfortable with desktop software toolchains, that makes sense. (And checkinstall is wonderful for not polluting your system with random unmanaged files). But I came at this knowing like embedded c++ and Python, and there was just a lot of tools I had to learn. Like what make was and how library files are linked/found, etc. And for someone who's not a developer at all, I imagine that this would be even harder.
I'm glad!