I believe that this is a default fallback.
Here are the restic options you can set. I believe that you can even set Minio options but I am not 100% sure about that.
restic options
All Extended Options:
azure.connections set a limit for the number of concurrent connections (default: 20)
b2.connections set a limit for the number of concurrent connections (default: 5)
gs.connections set a limit for the number of concurrent connections (default: 20)
local.layout use this backend directory layout (default: auto-detect)
rclone.args arguments for running rclone (default: serve restic --stdio --b2-hard-delete --drive-use-trash=false)
rclone.connections set a limit for the number of concurrent connections (default: 5)
rclone.program path to rclone (default: rclone)
rest.connections set a limit for the number of concurrent connections (default: 5)
s3.connections set a limit for the number of concurrent connections (default: 5)
s3.layout use this backend layout (default: auto-detect)
s3.retries set the number of retries attempted
s3.storage-class set S3 storage class (STANDARD, STANDARD_IA, ONEZONE_IA, INTELLIGENT_TIERING or REDUCED_REDUNDANCY)
sftp.command specify command to create sftp connection
sftp.layout use this backend directory layout (default: auto-detect)
swift.connections set a limit for the number of concurrent connections (default: 5)
Did you follow the documentation here?
https://restic.readthedocs.io/en/latest/030_preparing_a_new_repo.html#amazon-s3
Additionally, there is this guide: Examples — restic 0.16.3 documentation
It might be a bit outdated but maybe it’s still helpful.
I don’t have a S3 repo myself so I can’t give you more info than I found myself.
Another idea is to search the forum a bit for anything related to S3 and regions.