https://nucleus-coop.github.io/
I used this to play Minecraft with my girlfriend on my PC and it works alright. I do use it with 2 screens though. There’s other games too but I haven’t tried any.
But yes I do agree there is a severe lack of splitscreens nowadays especially with the hardware we have available now compared to what we used to.
Help join the cause if you havent
They got sold (sorry for reddit link) https://www.reddit.com/r/SimpleMobileTools/comments/187w64x/simple_mobile_tools_bought_by_zipoapps/
Use the fossify forks now (also on f-droid)
https://www.androidpolice.com/nova-launcher-acquired-by-branch/
Kind of old article, but yea, they were sold.
That’s been like 10 years by now or more