yes I did tried a lot of themes from gnome look but it only affect gtk3 softwares and maybe some gtk4 softwares, software like Gnome calculator, Easyeffects doesn't change a thing
Apple, Sony, N*****do, Netflix all use BSD but they don't contribute any code to the BSD project itself, because of the BSD allow other people/company to close source their code when using with BSD
Looking through your response I think you got unlucky updating bad packages causing it to not boot anymore, my advice is to boot Live USB backup your data and reinstall a distro with time shift just to be safe.
Thanks I'll give it a try, No I don't use Flatpaks I only use the AUR