My system, macOS with Apple M1 chip, is currently not supported by GDB.
To quote gdb-devel, "lldb is the way to go" to debug Emacs for me.

Attached patch adds rather limited support for that.  Limited by

- the fact that I don't know LLDB,
- that I don't know LLDB's Python API,
- that I'm not a Python programmer,
- that the Python API documentation is pretty lacking in itself,
- that I didn't implement support for ENABLE_CHECKING and what else
  might change Lisp_Object layout

So please bear with me.

Anyway, at least displaying some Lisp_Objects with 'p obj' seems to
work, and 'xbacktrace' seems to be working.

YMMV.