Hey James, welcome!
That’s a solid setup. Those Pi 5s and the N97 make a great combo for tinkering and home services. Totally get you on the Windows frustration; more of us are reaching that point lately. I spent a year thinking I could use Windows more than Linux as a daily desktop OS. Not possible.
Sounds like you’re already halfway over to Linux anyway, especially with the self-hosted projects you’re running. Looking forward to seeing how your Ubuntu server build goes and hearing more about your book too.