To offer some early feedback after playing with it for only a few hours, this seems to be working remarkably well. I installed with Open GApps 10 beta pico, and Magisk 20.1.
Battery life actually seems better than it was on LOS 15.1 (Android 8.1), though that could be because I dramatically slimmed down the apps I have installed (from ~150 to ~50). Overall, everything seems very smooth, fast, and efficient. It's a very refreshing experience, since this phone had been getting slower and slower.
I've had a couple apps freeze on launch, but closing and reopening always seems to resolve the issue.
I haven't figured out what GCam I'm going to use yet. I'm probably going to run through several of the suggested apks on Celso Azevedo' Google Camera Ports site until I find one that works reliably.
Visual voicemail in the phone app failed to setup, but that could be an issue with my carrier (T-Mobile). I haven't tried to troubleshoot that yet.
Everything else seems to be working great. Calls, GPS navigation, etc. No major issues.
This is amazing work, @PixelBoot. Thank you so much!
Do you get a random shutdown around 30-40%?