It's not quite what you describe but I'd argue it's very much what you're looking for. It runs Diablo 2: Lord of Destruction on Android with some quality of life mods and the option to mod it more heavily.
D2Lod is actually very different from D2 Resurrected or Eternal, mostly because it was made when games weren't live services. There were a lot of changed made to D2R that increased the grind which aren't present in D2Lod. It's the full game with an engaging story, cinematics, decent replayability, a solid gameplay loop, and you'll probably recognize the birth of a lot of familiar mechanics in it (borderlands is literally just d2 with guns)
It's a really reliable and open source app, I've been playing for weeks and it only crashed once on the very first run of the game, but I think that's because it took too long and graphene killed it. It does use the original d2Lod files which aren't open source but they were programmed for windows 95 so they're closed source like a picket fense is secure.
That is possibly the only issue I expect you'll have with the game, it's by no means retro but the graphics fit the age. Great for what they are historically but even I can see the improvements made for D2R. Lastly you do have to own a copy of D2Lod and use the cd keys to activate it. The github tells you how to get them officially but I'd be happy to just give you the files and keys from my 2001 Battle box. I bought the game and I'll gladly remind Blizzard of that every chance I get.