/usr/bin/sandbox-exec is still on macOS Monterey. It's not pretty, but you should still be able to roll your own sandbox rules and run any arbitrary app with it:
It's going away though and is less functional than in previous versions of the system. Basically a waste of time trying to build rules for it right now.
https://mybyways.com/blog/creating-a-macos-sandbox-to-run-ko...