Blender 5.2.2 imports cattrs and requests, and the package depends on neither.
On a sid system with blender installed (Recommends included), every start prints this and the core Extensions add-on stays off:

Traceback (most recent call last):
  File "/usr/share/blender/scripts/modules/addon_utils.py", line 544, in enable
    mod.register()
  File "/usr/share/blender/scripts/addons_core/bl_pkg/__init__.py", line 986, in register
    _remote_asset_library_restore_backups()
  File "/usr/share/blender/scripts/addons_core/bl_pkg/__init__.py", line 580, in _remote_asset_library_restore_backups
    from _bpy_internal.assets.remote_library import listing_downloader
  File "/usr/share/blender/scripts/modules/_bpy_internal/assets/remote_library/listing_downloader.py", line 32, in <module>
    from _bpy_internal.http import downloader as http_dl
  File "/usr/share/blender/scripts/modules/_bpy_internal/http/downloader.py", line 51, in <module>
    import cattrs
ModuleNotFoundError: No module named 'cattrs'
Exception in module register(): /usr/share/blender/scripts/addons_core/bl_pkg/__init__.py

The same code imports cattrs.preconf.json, and json_parsing.py and cli_listing_generator.py in the same directory import cattrs too.
With python3-cattr installed, the add-on fails at the next line of downloader.py, `import requests`.
With python3-cattr and python3-requests installed, Blender starts without the error, in the background and with its interface.

Reproduce: in sid, `apt install blender`, then `blender -b --factory-startup --python-expr 'import bpy'`.

Versions: blender and blender-data 5.2.2+dfsg-1, python3 3.14.7-3, python3-cattr 26.2.1-1, python3-requests 2.34.2-1.

Adding python3-cattr and python3-requests to blender's Depends would fix it.

I found and checked this with the help of an AI assistant (Claude); the runs above are in our test containers on Debian sid.

Daniel


These runs were in a Debian sid container; the kernel shown is the host's.