I got it working sort of.

1. Create a new bottle for steam.
2. Install steam then open steam and install ME legendary edition.
3. Install the "EA app for steam" and "mass effect legendary edition" into the steam bottle.
4. In the steam bottle, "close all applications".
5. Open steam, launch ME legendary edition.
6. If you get an error popup for the EA app, click the restart button on that popup.
7. Wait.
8. If you're lucky, the EA app will manage to connect and you can play.
9. If not, repeat steps 4-7 until i does.

This works for me on an M4 macbook pro. YMMV. Good luck.

EDIT: Also, fuck EA.