You could use Synctrain or maybe Möbius Sync to SyncThing-sync a folder with your phone, then use Strongbox or KeePassium or any other KeePass-compatible app to work with the file?
mbirth
I'm using Strongbox on macOS and iOS. Uses a KeePass2 database in the background, does TOTP (so does KeePassXC), syncs via iCloud (but also supports SFTP, WebDAV, OneDrive, Google Drive, and Dropbox) and also keeps my Passkeys. And it supports Apple's AutoFill API, so it works in basically any input field across the systems and feels "native". No browser extensions (at least for Safari) needed.
And if it goes rogue, I can switch to e.g. KeePassium or any other KeePass-compatible app.
I had looked into GRAV which is not quite suited for blogging (i.e. date-based posts) but rather for wiki-like content or a simple page structure. Also, they're also feeling more and more enterprisey, especially with their recent 2.x release.
Tried Serendipity but found it to be more or less on life-support.
And finally settled on a very basic WordPress with only a handful of plugins (all set to auto-update), most importantly SQLite and ActivityPub. Backups are a simple copy of all the files or just the SQLite db. The Gutenberg post format in the SQLite db is easy enough to convert it to anything else using a small custom Python script should need be. I don't remember how I imported my existing posts, though. Might've been via RSS import.
On clients you mostly have to set MODE=netclient in the nut.conf and modify the upsmon.conf according to the manual and detailed manual. By default, it should only shutdown systems when reaching a "low battery" situation, not immediately when switching to battery power.
What was the difficulty with NUT for you? The setup is pretty straightforward, IMHO.

Should be easy to wrap in a container, too.
THIS! Normally, the battery should be accessible via some door or a few screws. Replace the battery for a few bucks and you'll have 5 more years of peace.
If you search for "12V ups" there are several. However, most only go up to 2 Amps. Not sure what kind of monster router actually needs 5 Amps, though. Also, I believe those 12V UPSes don't provide status information via USB. So, there's no way to know when the battery backup is going to fail.
You're talking about someone that had her floor in the EU building fortified, only allowing access for a few selected people. Does that look like she intends to improve her reputation to you?
$ strings "PSOFT Pensil+ 4 Render App.app/Contents/MacOS/Pencil+ 4 Render App (Trial)"
...
pshi_%s.dat
psh_%s_%u.tmp
psh_%s_%u.dat
/Users/Shared/.etc
So, maybe check the /Users/Shared/.etc folder? Make sure to turn on hidden files in Finder by pressing ⌘⇧. (dot)! Also, look for some files starting with psh_.
EDIT: I've also seen something like /.config/ or /.config/PSOFT/ - so might be in your user directory or in the /Users/Shared/ one.
A buddy just shipped a pre-configured Comet Q to their parents.