I just wanted to add to this post of mine with instructions on how to use iDrive’s E2.
There appears to be a thing that iDrive has recently switched on that causes access keys that are assigned only to one bucket to fail unless a bucket auth check is bypassed.
You can bypass this when using rclone with no_check_bucket = true in the rclone.conf file, but I’m not sure such an ENV setting exists for Discourse building.
As a result, with iDrive E2, you currently must use a key that has access to write to all your buckets, rather than just one.