When starting borgmatic config generate, I get the error :

# borgmatic config generate
Generating a configuration file at: /usr/local/etc/borgmatic/config.yaml
Traceback (most recent call last):
  File "/usr/local/bin/borgmatic", line 33, in <module>
    sys.exit(load_entry_point('borgmatic==1.8.2', 'console_scripts', 'borgmatic')())
  File "/usr/local/lib/python3.9/site-packages/borgmatic/commands/borgmatic.py", line 872, in main
    list(
  File "/usr/local/lib/python3.9/site-packages/borgmatic/commands/borgmatic.py", line 657, in collect_highlander_action_summary_logs
    borgmatic.actions.config.generate.run_generate(
  File "/usr/local/lib/python3.9/site-packages/borgmatic/actions/config/generate.py", line 25, in run_generate
    borgmatic.config.generate.generate_sample_configuration(
  File "/usr/local/lib/python3.9/site-packages/borgmatic/config/generate.py", line 278, in generate_sample_configuration
    schema = yaml.round_trip_load(open(schema_filename))
  File "/usr/local/lib/python3.9/site-packages/ruamel/yaml/main.py", line 1127, in round_trip_load
    error_deprecation('round_trip_load_all', 'load')
  File "/usr/local/lib/python3.9/site-packages/ruamel/yaml/main.py", line 1037, in error_deprecation
    raise AttributeError(s)
AttributeError: 
"round_trip_load_all()" has been removed, use

  yaml = YAML()
  yaml.load(...)

instead of file "/usr/local/lib/python3.9/site-packages/borgmatic/config/generate.py", line 278

    schema = yaml.round_trip_load(open(schema_filename))

There are more recent versions upstream, they may have corrected this ?