Wait until it affects me. Just like when I ditched Chrome. Just like when I ditched Windows. I used Vanced long after they were stopped, didn't switch to ReVanced until Vanced literally could not play anymore. I'm the latest adopter, for sure. By the time I make a change, the path of what I want to do has been well-tread by others.
So you're ditching Android, for what? Is there an actual Linux phone you're looking for, are are you gonna carry around a pocker-sized PC? (genuinely asking)
Don't know yet! I would assume get a phone that supports Graphene or Lineage. But I'm not opposed to some PDA sized Pi Zero Frankenstein abomination if it does what I want it to.
That device didn't meet the requirements for GrapheneOS even when it was supported by the OEM. As of now, it is an EOL device and is highly insecure.
https://grapheneos.org/faq#future-devices