After many hours staring at logs and trying to reproduce/debug an issue that seemed to happen once every dozen or so boots... I miiiiiight have a fix for the Google Pixel 3a rotation sensor being inverted on #postmarketOS... If you have one of these devices and are running pmOS edge, please help me test this 
https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/7681
Can be tested with: doas apk add mrtest && mrtest upgrade 7681