Unable to run docker container as other user

I am trying to run the docker seafileltd/seafile-mc:11.0.5-arm as another user.
My docker-compose looks like this:

image: seafileltd/seafile-mc:11.0.5-arm
user: 1007:1007

However, as soon as I place the user: line in the docker-compose, seafile will not start:

$ docker logs seafile
*** Killing all processes…
Traceback (most recent call last):
File “/sbin/my_init”, line 414, in
File “/sbin/my_init”, line 330, in main
import_envvars(False, False)
File “/sbin/my_init”, line 90, in import_envvars
for envfile in listdir(“/etc/container_environment”):
File “/sbin/my_init”, line 74, in listdir
return sorted(os.listdir(path))
PermissionError: [Errno 13] Permission denied: ‘/etc/container_environment’

The same user: directive in the same docker-compose for the containers mysql and memcached give no problem; it is the seafile container that doesn’t seem to like it.

I have docker running as non root. The problem I am trying to solve is that the files created in the seafile-data folder are not owned by the user running docker.

Can anybody help? TIA.

Did you follow this instruction: Seafile Community Installation - Seafile Admin Manual

Thank you for you reply @daniel.pan and for the link
I am in a shared hosting environment. I can´t add a user and group with those specific id’s.
Is the usual way (instructing docker with the user: directive, as working with p.e. memcached and mysql) not available for seafile / why is docker ignoring this directive?