Windows isn't immutable either. And i had a lot of issues with Kinoite. Some flatpaks need workarounds, everything starts only after a second, can't really remove that one annoying software and too much rpm-ostree installs slows updates to a crawl, etc. Then you look into Universalblue's build-your-custom-image and see the bazillion steps and dependencies and walk away.

Now i look into plain old Fedora as a Windows 10 alternative for my mom.