Back to the days I was fixing a lot of computers of friends and relatives, my Swiss army knife of Linux was https://www.system-rescue.org/
Very lightweight but with a full set of recovery tools. I’ve tried it recently and I still find it up to the expectations.
I’ve also used a fair amount of https://clonezilla.org/ to (re)store images of freshly installed OSes (mostly windows XP and 7 to give you an idea of the timeframe) for people who I know would have messed up faster.
A lot of technical aspects here, but IMHO the biggest drawback is liability. Do you offer free storage connected to internet to a group of “random tech nerds”. Do you trust all of them to use it properly? Are you really sure that none of them will store and distribute illegal stuff with it? Do you know them in person so you can forward the police to them in case they came knocking at your door?
Yes, you can do it on your server with a simple iptable rule.
I’m a little rusted, but something like this should work.
iptables -t nat -A PREROUTING -d [your IP] -p tcp --dport 11500 -j DNAT --to-destination [your IP:443]
You can find more information searching for “iptables dnat”. What you are saying here is: in the prerouting table (ie: before we decide what to do with this packet) tcp connections to my IP at the port 11500 must be forwarded to my IP at port 443.
For automatically unlock encrypted drives I followed the approach described in https://michael.stapelberg.ch/posts/2023-10-25-my-all-flash-zfs-network-storage-build/#auto-crypto-unlock
The password is split half in the server itself and half in a file on the web. During boot the server retrieves the second half via http, concatenates the two halves and use the result to unlock the drive. In this way I can always remove the online key and block the automatic decryption.
Another approach that I’ve considered was to store the decryption keys on a USB drive connected with a long extension cable. The idea is that if someone will steal your server likely won’t bother to get the cables too.
TPM is a different beast I didn’t study yet, but my understand is that it protects you in case someone steals your drives or tries to read them from another computer. But as long as they are on your server it will always decrypt them automatically. Therefore you delegate the safety of your data to all the software that starts on boot: your photos may still be fully encrypted at rest so a thief cannot get them out from the disk directly, but if you have an open smb share they can just boot your stolen server and get them out from there
QNAP sells extensions unit https://www.qnap.com/en/product/tr-004
They usually connect with USB (at least for home grade devices), but my understanding is that they are not seen as block devices so the nas has access to all the single drives like they were internal.