As long as it’s not an exit node, nobody will be able to tell what the traffic is. It’s all encrypted including the metadata.

I think they mean uPnP

How does that increase the risk compared to something like JBOD or overlayfs? In both cases you will lose data if a drive fails. Keep in mind that this is btrfs raid0, not regular raid. If anything that decreases the chance of corruption because the metadata is redundantly stored on both drives.

No mention of systemd? This is unacceptable.

A disk failure will cause you to lose data, yes. But that’s also the case in all the other solutions discussed here. Backups should be handled separately and are not part of the original question.

Have you considered simply setting btrfs to RAID 0?

Even if you computer is not exposed to the internet: are you certain that every other device on the network is safe (even on public wifi)? Would you immediately raise the alarm if you saw a second printer in the list with the same name, or something like “Print to file”? I think I personally could fall for that under the right circumstances.

Is this a threat?

“Safe” being defined in a user-hostile manier, i.e. with unmodified Google components and not rooted.

“Google-controlled” would be a better word.

With this approach you would lose the subvolume structure and deduplication if I’m not mistaken.

No, you got downvoted because you were insulting and incorrect.

The most common physical attacks will be you misplacing your device or some friend/burglar/cop taking it. FDE works great in those scenarios.