That will be in one of the next 2.8 betas. Unfortunately it isn’t ready for the upcoming 2.7 release yet.
I’m sorry I didn’t see your cry for help earlier. Here’s a tip for everyone else who struggles with uploads stored on S3 messing up a restore: Extract the dump.sql.gz file from your backup and rename the file. E.g. when the original backup was discourse-2020-10-09-133921-v20201007124955.tar.gz then the resulting file should be called discourse-2020-10-09-133921-v20201007124955.sql.gz. Restoring that file should work.