ET: Legacy still get updated, it may not have super high resolution, but it just recently got a new renderer. Still campatible with the last official release, though the ingame server browser have not worked the best for me compared to finding server through verious online sites.
I have massive respect for what these selfless volunteers are doing, but progress has been slow. I wonder whether it would make sense to do a crowdfunding campaign to hire an actual gamedev studio to port the gameplay to a modern engine, and/or an art house to recreate all assets from scratch to modern standards?
https://www.etlegacy.com/