Specifically:

1. The Dark mod (https://web.archive.org/web/20161010014521/http://thedark5.com/)
2. Ulmo's Stash
3. Diablo clicker

I've been told it doesn't, but I wanna make sure.

1. If I recall correctly, The Dark provides its own executable download, so it only needs the Hellfire data. Therefore, this should work, to the extent that Hellfire v1.01 would work on modern systems.
2. This will probably work, since GOG distributes something very close to the original game.
3. I believe this was just a mouse button clicker intended for use with Diablo, so it should work fine.

Also, I should note that utilities may be superseded by Qualify-of-Life features in DevilutionX. That won't help with getting a mod working, though.