What do you mean? I don’t think any other operating system even comes close to Windows in regards to backwards compatibility. Most software designed for Windows 98 will still run fine on Windows 11.
There are thousands lines of code in the NT kernel with patches for specific programs. There is even a line patching an incompatibility with Lego Island, lol.
I don’t know any open source client that is even remotely as nice to use as Boost. Also, it’s not like the developer is actively spying on you, that’s just the default AdMob popup Google is now forced to show (They simply didn’t ask for any kind of consent in the past).
Anyway, I simply paid a few bucks for ad-free Boost.