I just realized something, in every version of TmnT with an apocalyptic future, Donatello has been dead or missing and assumed dead...
Last ronin - died fighting the foot
2003 SaiNW - missing and presumed dead by present him.
2012 mutant apocalypse - died during the blast and is now a robot so semi alive I guess...
2018/rise apocalyptic future - died of unknown causes but knowing him, it was while fighting.
Not to mention that Donnie had the same 2012 apocalypse treatment in the IDW comics and his body died while he inhabited Metalhead
and in 2012 April killed him before bringing him back!
It's also apparently implied he died of old age post Mirage comics, but I haven't read that far so correct me if I'm wrong
If anybody's curios, this is the total death count between the turtles:
Also for those wondering Splinter has 6 deaths, which depending if you count the mirage donnie death or not either puts Donnie at having more or the same amount of deaths as his father!