This is the only question that really matters. If it’s overpriced? meh, it’s a cheap alternative to a NUC. But if it’s going to be stuck on obsolete software forever, run.

I used stunnel years ago to tunnel both openVPN and SSH traffic and it worked flawlessly. Looks just like https web traffic to dpi software. Beware though, that long open connections can also set off flags, so don’t keep connection’s open permanently.

Car batteries are cheap storage if you very rarely discharge them. You get many years if you are only using the top 80% or so of their voltage range, but if you discharge them to 50%, you only get a few hundred cycles, and if you discharge to 0%, you get dozens, if that. “Deep cycle” batteries have the same characteristic, but tend to give you more amp-ours before you hit those thresholds.

Good Lifepo4 batteries could last up to 10 years with daily full discharges. They are quite amazing in that respect. They are also likely safer than even lead acid -which need to be vented properly to avoid hydrogen gas buildup. They don’t get thermal runaway like lipos, but the cells are very much capable of producing enough current for electrical fires, so you want ones that are built properly. Maintenance is pretty much just “don’t ever charge it if it’s frozen.”

DIY, all DC is often the way to go if you are trying to run for a long period of time. UPSs are really typically designed to run just long enough ride out brown-outs or to shut everything down safely in a total blackout. Some even shut down if they don’t sense a heavy enough load (i.e., designed to assume servers have shut down, and so preserves the battery -I banged my head against that for so long!).

I have everything on a consumer-grade APC now, and I have it set up to give me about 3 minutes of server, + another half hour of basic networking. I do have some marine deep cycles and an inverter, so I could set up the networking to run longer if cell towers were down and I needed it. But I’d likely use the energy for other things.

I like this approach, but I’m currently sitting in a foreign hotel who’s wifi seems to block WG. Annoying. Keep a TLS-protected reverse proxy for things you might need through obscure networks.