You don't have to use the latest OS.
Yes, Tahoe will be the last. However that will last you another year and then you'll get a couple more years of security updates after that, so it will still be safe to use. The thing is already >10 years old so hopefully you can find a suitable replacement before then.
Putting Linux on a Mac is, in my experience, a right pain in the ass. They have proprietary hardware and drivers that just make it very painful.