Agree. I have been modding my phones for years becuz of google and other companies doing things like the anti-rollback, no way to unlock bootloader, and others. It getting difficult to do so.Thanks for that heads up, so it looks like going backwards to a Miui ROM is probably more hazardous than it's worth at this point. Worst case scenario I do end up bricking the phone (if I haven't already) and have to send it to someone with an EDL to fix.
The article mentions something about having to flash a dummy image to pass something to antirollback before TWRP can be successfully run. I wonder if this is why I can't successfully boot into recovery?
No idea, all I know is this is a bigger PITA than any of the other phones I've ever flashed, and the first one that I may have bricked.
If all you did was flash the boot/recovery, you should be fine. I was in the same state. As I said, download the PixelOS recovery and do
fastboot set_active a
fastboot flash boot recovery <PixelOS recovery file path>
fastboot reboot recovery
and see if that works. Then, you can at least adb sideload images.