I've jumped through a couple of unexpected hoops to get here, following some suggestions online: I've used DevToolsSecurity -enalble, and I've used dseditgroup -o edit -a me -t user _developer to put myself in the _developer group. That has at least got lldb past the "process exited with status -1 (developer mode is not enabled on this machine and this is a non-interactive debug session.)" problem. I'm also running through VNC, rather than ssh, so that I can see pop-ups and new windows, but my preference is for ssh.
The crash that I'm trying to debug is in some numpy function in a python program that is spawning multiple threads, so it's relatively hairy, but my past experience has been that running code under lldb results in return to lldb when the program segfaults, but with this code, on this machine, lldb just unhelpfully says that the workers exited with SIGSEGV(-11) and the Problem Report screen pops up to send the results to Apple.
I don't want or expect Apple to debug this problem. I want to do it myself. How do I stop the Problem Report app from taking control?
FWIW the python that I'm running is 3.8 installed from MacPorts, but the numpy is running from a venv and was installed by pip according to a project's requirements.txt.