Restore RethinkDB backup on MacOS Big Sur

Question

My local Rethink database disappeared after upgrading to MacOS 11 (“Big Sur”). But that's alright, as I have a backup. But I can't, for the life of me, restore it.

rethinkdb restore [file] and rethinkdb import [file] didn't work, but after some googling I found that I had to install the python tools (pip3 install rethinkdb). I did that, but now I get this error:

% rethinkdb restore rethinkdb_dump_2020-11-21T20:35:20.tar.gz > bug.log
Traceback (most recent call last):
  File "/usr/local/bin/rethinkdb-restore", line 10, in <module>
    sys.exit(main())
  File "/Users/$USER/Library/Python/3.8/lib/python/site-packages/rethinkdb/_restore.py", line 339, in main
    do_restore(options)
  File "/Users/$USER/Library/Python/3.8/lib/python/site-packages/rethinkdb/_restore.py", line 315, in do_restore
    _import.import_tables(options, sources)
  File "/Users/$USER/Library/Python/3.8/lib/python/site-packages/rethinkdb/_import.py", line 1359, in import_tables
    progress_bar.start()
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/context.py", line 283, in _Popen
    return Popen(process_obj)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 32, in __init__
    super().__init__(process_obj)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_spawn_posix.py", line 47, in _launch
    reduction.dump(process_obj, fp)
  File "/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/multiprocessing/reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle '_thread._local' object

I've tried to uninstall RethinkDB and the Python tools and reinstall both. Same outcome.