Surprisingly, Kalifornia has a good system...the issuer of the death certificate notifies the appropriate registrar.
My Dad died not long before absentee ballots went out for some election (he and Mom were both permanent absentee voters), and no ballot came under his name - and I was watching for it, for sure!
I hope it didn’t go somewhere else :(
Near the end of her life, my Mom moved from the East Coast, to Seattle, to be close to my sister. When I went up to visit, I asked her why she didn’t register to vote. “I’ve voted Republican all my life, I don’t want to be voting Democrat, after I die”.