hi,
without a debug log, hard to know what th exact issue.
looks like no multi-part upload and chunk size for koofr.
as compared to https://rclone.org/s3/#multipart-uploads
and based on this topic, might try --disable-http2
https://forum.rclone.org/t/multithread-upload-speed-slowed-down-to-single-thread-speed-for-koofr/35427