Soo I'm getting back into UO after a 6 year break -- making a shard for just myself and 5-6 other friends to play on. Started with RunUO, realized it didn't have the quests for Stygian Abyss in place, and so I posted on their forums looking for answers and was pointed here. Just downloaded ServUO and compiled it, spawned the world, and see that there are quite a few of the quest NPCs and such. I noticed there are still a few things missing, such as the SA dungeon isn't fully spawned, but I will explore the forums on how to fix that issue. I have some questions regarding it, but I'll post those on the correct forum once I'm verified. Anyways, I look forward to playing again and it appears that people here are quite helpful so I'm glad to see that :)
Welcome here!

SA is not 100% but we are the closest. You might want to look for the SA mini champs in the releases sections, its probably part of what you are missing.
I think I found what you are talking about in custom releases. Just waiting to get verified to download it. Thanks for the help!