Can you check the permissions on that directory in your docker host? I suspect either /ps/config/PhotoStructure is 755, or /ps/config/PhotoStructure/settings.toml is 644, and that both are owned by root.
If you were using v0.9.1, PhotoStructure was probably running as root.
I added linuxserver-style PUID and PGID support to the PhotoStructure docker image a couple alpha builds ago. If you’ve got UID or PUID set, the v1.0.0 docker image now tries to run as that user id, which may not have read or execute permission for that bind mount path.
You can set UID=0 and GID=0 in your environment: section to disable this, if you don’t want to hassle with chowning stuff on your host machine.
In the meantime, I’ll look into improving this error message!