Open Dolphin, the one you use for rollback/slippi(and make sure its up to date), and right click your vanilla Melee iso, then click “open containing folder”. See where your vanilla ISO is stored in your computer.
Once you’ve found your Melee ISO, drag it anywhere on the patcher window.
It will generate "BeyondMelee-1-1-1.iso" in the same folder as the patcher if everything went right. (Diet-Beyond for the diet version)
Put this iso in the same folder as your vanilla Melee iso, and then refresh Dolphin. Beyond Melee should show up as a separate ISO, no the vanilla one.
You should be good to go.
If you still have any problems, make sure to first check the FAQ.
(optional) This step is just for finding your vanilla ISO, if you know where it is, skip it.) Open Dolphin, the one you use for rollback/slippi(and make sure its updated), and right click your vanilla Melee iso, then click “open containing folder”. See where your vanilla ISO is stored in your computer.
For the first field, find the patch with the extension ".xdelta" in the folder you downloaded it to.
Second field, put in your vanilla ISO you just found in your Dolphin.
Third field, browse to the folder your vanilla ISO is in, then put in Beyond-Melee-1-1-1.iso (or Diet-Beyond). Click Save.
Patch.
You’re good to go and have Beyond Melee installed on Mac!
If you still have any problems, make sure to first check the FAQ.
How to install on Linux:
Download xdelta for your distribution. It will likely be available through your package manager under the name xdelta3