https://mullvad.net/en/blog/2023/8/9/response-to-tunnelcrack-vulnerability-disclosure/ is Mullvad’s response to this topic. TLDR not a concern other than possibly for IOS.

Thanks for pointing out dar, out definitely has some very interesting capabilities. My backup took off choice is BorgBackup as it makes local/remote, encrypted, deduplicated backups easy and allows for mounting previous snapshots via fuse fs for easy restore.

Instead of a fire safe which will only offer some protection I would rather get two Pelican style cases. Keep your backup drive(s) in there. Use a deduplicating/encrypted backup software to create two backup sets (I highly recommend BorgBackup). Store one of the backup cases off-site (at a friend’s house, in a drawer at work, …) and occasionally rotate the two cases.