So, there are projects like these;

https://www.dfworkshop.net/

https://vcmi.eu/

https://github.com/ihhub/fheroes2

https://zdoom.org/index

Projects that in one way or another aim to modernize a classic, or try make it more playable on modern machine, or just try to expand on things (like gzdoom does)

what other projects are out there in a similar vein?

I find this a little difficult to search for, even with specific terms (i tried finding myself)