I read a lot about the problems that MacOS 10.15 Catalina brings to emulators. Before moving my iMac to this system, I started some compatibility checks with a MacBookPro 13'' Mid 2012. This is limited to compatibility and issues, but not performance, since this MacBookPro never ran MAME very well.
General recommendations: If you want to install emulators outside of $HOME/Documents, you need to unlock this directory in System Settings/Security/Full Disk Access. If I understand correctly, not only the Applications, but also directories must be granted Full Disk Access to work.
If something does not work immediately, in particular immediately after upgrading to Catalina, do a system restart. Interestingly this resolved a lot of issues for me.
MAME 0.217 Official Mac Build: No issues at all, everything runs as expected. I also moved the mame directory from $HOME/Documents to a newly created $HOME/Games. After granting Full Disk Access to this directory, everything worked as expected.
Attract Mode 2.6: I read things that Attract Mode does not work in Catalina. But for me, everything seems to work, and I did the following:
- The Application must be whitelisted in System Settings/Security (same Gatekeeper procedure as under MacOS Mojave)
- The hidden directory $HOME/.attract must be granted Full Disk Access.
- In my case it helped tremendously to restart the system.
- In my MAME 0.217 test system, I could successfully create a romlist and install the cosmo-arcade theme.
Update 19 January 2020: I updated to Attract Mode 2.6.1 and all remains fine. It is a worthy upgrade, in my preliminary tests, the MAME scraper now work quite well (but for limited games, though). So it is definitely a worthy upgrade.
Retroarch 1.8.3: As stated in the Libretro forum, the Metal build does not load cores due to codesigning issues. Interestingly, the OpenGL version of Retroarch for MacOS does not seem to have this problem. FinalBurn Neo downloads and starts games, and so does MAME (current, actually 0.214 currently).
Conclusion so far: The security features of MacOS increasingly become an issue for software that is developed outside of the Mac Store. While I get everything running so far, you see how many strides developers must do to further develop apps for MacOS. This might become a problem and could force me to switch to Linux or even Windows.