Are you using stock Docker compose setup?
No; I am running under Docker on Synology NAS but not using compose. Based on the error I believe this is a (minor) code issue. This is mostly an informative post as I didn’t get any search results on phpqrcode and it doesn’t seem to have any impact on functionality.

If not, either reproduce this issue on the official demo or switch to Docker and see if the issue is resolved.
Not able to do this since the demo doesn’t provide necessary access.

Describe the problem you’re having:
cannot delete non-empty directory: lib/phpqrcode is logged to stdout during container startup. I think this is associated with file cleanup from commit https://git.tt-rss.org/fox/tt-rss/commit/3fd785654372d493c031d9b541ab33a881023a32

Include steps to reproduce the problem:
Update from commit prior to above to commit equal to or later than above.

tt-rss version (including git commit id):
v21.03-f4d0e7b

Please provide any additional information below:
I stopped the containers, manually moved that folder from the docker volume, and restarted container which is what I’m guessing gets to the same intended result.