I don't think he is in jail or dead.
As everything in crypto is hidden with many keys, we probably we will never know why he disappeared. The most probable reason is, yeah, he is dead, many months already and this is not due to covid, his eth in fees is untouched.
What are his dev mining addresses again? I am too lazy to start the miner and fetch them. From what I remember he used something like a Coinbase address for his fees so impossible to tell if he hodl'd the coins or sold them immediately.
If you are right, then it is rather odd that his ETH is untouched when ETH went to almost $500 a few months back. Really irresponsible not to at least take some profit off the table at $500 when we dipped below $100 a few times in the past.
Does anybody have a problem with ultra low hashrate on ETH mining with 4GB GPU?
Your GPU is running out of memory due to growing dag. Switch to Linux and use Phonixminer instead and it will work for another 1 month and then you can't mine ETH anymore.