Has Tarsnap become inadequate, security-wise? The service may be expensive for a standard backup. It had a serious bug in 2011, but hasn't it been adequate since then?

I don’t know anything that makes me think it’s inadequate per se, but it’s also been more than 10 years since I thought about it. Restic, gocryptfs, and/or age are far more flexible, generic and flat out better in managing encrypted files/backups depending on how you want to orchestrate it. Restic can do everything, gocryptfs+rclone can do more, etc.