Hi,
Thanks for bringing this up!
All the DAWs I had tried so far didn't complain, but I tried it now in Ableton 12 and get the same result as you are.
So the root problem really is that I didn't get around to sign my plugin yet .. that's something I should eventually do to avoid Mac flagging the plugin as quarantined. That's what's stopping Ableton from loading it.
There is a solution though:
First you'll have to use a terminal to manually remove the quarantine flag from the bundle.
Someone already made a video that shows how:
With the quarantine attribute removed, Ableton should no longer complain about the plugin.
Simply go to Live -> Settings -> Plug-Ins and find the Rescan button, and click it while holding the option/alt key.
That will do a hard rescan, so it will also rescan plugins that it previously failed to scan.
This makes it work on my setup, I hope it works for you too!