These devices have been recommended in the past, and it looks like they can run OpenWRT

https://www.amazon.com/GL-iNet-GL-SFT1200-Secure-Travel-Router/dp/B09N72FMH5

https://openwrt.org/toh/gl.inet/start

I would probably use ntfy.sh for this purpose. It doesn’t quite meet all your requirements, but you could use a random channel name and get some amount of security…

You can self host it, or use the hosted version. (I know it’s technically not chat, but it works on a series of messages, it just happens to call them notifications.)

I don’t bother stopping services during backup, each service is contained to a single LVM volume, so snapshotting is exactly the same as yanking the plug. I haven’t had any issues yet, either with actual power failures or data restores.

I know it’s not ideal, but if you can afford it, you could rent a VPS in a cloud provider for a week or two, and do the download from Google Takeout on that, and then use sync or similar to copy the files to your own server.

The DMA doesn’t seem to have ever been about consumer choice, it’s about the choice of other competitors to have access to Apple’s customers without having to play by Apple’s rules. Just look at who was pushing for sideloading on iOS, I mostly saw Meta and Epic Games at the forefront. Why should Apple compromise my device’s integrity so that Meta can spy on me? I have no good answer to that.

My recommendation would be to utilize LVM. Set up a PV on the new drive and create an LV filling the drive (wit an FS), then move all the data off of one drive onto this new drive, reformat the first old drive as a second PV in the volume group, and expand the size of the LV. Repeat the process for the second old drive. Then, instead of extending the LV, set the parity option on the LV to 1. You can add further disks, increasing the LV size or adding parity or mirroring in the future, as needed. This also gives you the advantage that you can (once you have some free space) create another LV that has different mirroring or parity requirements.

If you want to change the name of the directory without breaking your volumes (or running services, etc), you can specify the name of the project inside the compose file

TiddlyWiki might be a good option. Technically it’s a wiki, but it is a single HTML page with all functionality built in JavaScript, you could host it on GH pages, though you wouldn’t be able to use its save feature there (you would have to save to your local machine and the deploy a new version). It stores text in little (or large) cards which can be given a title, tags and other metadata, and it providesa full search system.

Not that I’ve done this, but an IR sensor would probably work well.

I backup to a external hard disk that I keep in a fireproof and water resistant safe at home. Each service has its own LVM volume which I snapshot and then backup the snapshots with borg, all into one repository. The backup is triggered by a udev rule so it happens automatically when I plug the drive in; the backup script uses ntfy.sh (running locally) to let me know when it is finished so I can put the drive back in the safe. I can share the script later, if anyone is interested.

It’s been added recently, in the form of External Libraries.

Something that LVM supports but ZFS and BTRFS don’t, is the ability to reduce your storage. (That is, to empty and remove a drive from the array, without having to completely destroy the storage array.) As a home user without sufficient storage to have complete duplicates of everything, I find this an important feature.