Great news – (from 70 year old pensioner) - I did my first ROM phone flash via ubuntu 16.04 LTS of GrapheneOS without bricking new Pixel 3a! (£234 Ebay Auction)
It’s quite shocking to do so much to end up with far, far less. (far less Cr4p)
Then LOCK the boot!
Having only used Terminal to stop Avahi before it was good to be able to copy and paste from a LibreOffice Writer file itself copied and pasted from the instructions under the Yewtube video to eliminate risk of a typo. Best tip was to use tab after typing first few letters to automatically find install file as it changes with each update.
Yes quite easy, if not exhausting and mentally draining with the risk of bricking brand new phone – Phew!
Now need to find out how to transfer contacts and customise phone…