Technically this doesn't apply to me any more because recently I switched to Win 10 on a Bootcamp partition, after getting a new MacBook with Catalina. But I only took that route because I wanted runs to be as fast as possible. Virtual environments under Mac weren't quite ideal for that.
Generally I had always preferred running natively under Mac OS, so before resorting to the above I tried a few VM options. My favorite solution by far was Codeweavers' Crossover. There's a
14 day free trial version, but it costs 60€/equivalent otherwise. If you're willing to spend that I can definitely recommend it. It worked almost perfectly really, just the occasional FPS spike, but otherwise it's barely noticeable that D2 is not running natively.
Using GoMule natively under Mac OS was no problem either, I only had to dig a little in the Crossover folders to find the save folder. I didn't get commands like -ns etc. to work, though (which would also apply to RWM I guess). I'm not very tech savvy though so there's a good chance someone else will be able to get it to work easily.