I made one such lightweight alternative frontend: https://github.com/mickael-kerjean/filestash
I've been running filestash in front of sftpgo (using a combination of s3 and nfs for file backends) for a couple years now and have been very happy with it.
I've been running filestash in front of sftpgo (using a combination of s3 and nfs for file backends) for a couple years now and have been very happy with it.