I've added a standalone patch from the merged MR for older versions of tmgmt (in case you cannot use the latest one for some reason).
Full error:
User deprecated function: Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of tmgmt_local_translation_form_element(). See https://www.drupal.org/node/1831138 in Drupal\Core\Theme\Registry->processExtension() (line 498 of /app/web/core/lib/Drupal/Core/Theme/Registry.php)
Fixed
1.0
Translator: Local
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
I've added a standalone patch from the merged MR for older versions of tmgmt (in case you cannot use the latest one for some reason).