You may also configure rclone with Storj S3 (you need to have BypassGovernanceRetention permission in your S3 credentials) and use this method:
rclone purge us1-gw-mt:my-locked-bucket --header "x-amz-bypass-governance-retention:true"
However, it requires that you know the encryption phrase.
The other method would be using uplink not older than Release v1.124.6 · storj/storj · GitHub
uplink ls --encrypted --recursive --all-versions sj://locked-bucket/ -o json | jq '"uplink rm --encrypted --bypass-governance-retention --version-id " + .versionId + " sj://locked-bucket/" + .key' -r | bash