Installing the beta? This is the one place for install questions.
Post what you see on screen, word for word, plus your Mac (M1, M2, M3 or M4) and your Live version. I answer here in public so the next person doesn't have to ask.
Three things that fix most installs:
1. Quit Live before you run the installer.
2. In Terminal it's the word bash, one space, then drag the file in. Hit Return once, at the end.
3. AbletonMCP not in the Control Surface list? Your User Library lives somewhere else. The fix is on the install page.
— DSG