It can be removed[5], with some effort, though. Given its use in various electronics it wouldn't surprise me if some other UPSes use it, though have only seen discussions about Cyberpower.
[1] https://sound-au.com/articles/yellow-glue.htm
[2] This thread had various videos from users showing the arcing on Cyberpower units: https://web.archive.org/web/20220715134034/https://old.reddi...
[3] https://www.youtube.com/watch?v=9gqBzLNMFe4
[4] https://news.ycombinator.com/item?id=31954938
[5] https://www.eevblog.com/forum/beginners/how-to-remove-the-dr...
But manufacturers don't use it. Maybe they haven't redesigned after the price dropped. Or maybe cause prices is still too high. I think LiFePO4 would be most useful for rack mounts, or small UPSes that aren't possible with lead acid.
Generally lithium UPS win in a 10-year TCO, but SLA wins in up-front costing. Which leaves us with two issues - most consumers look at the sticker price not the TCO, and no-one wants to market their products as "Our lead acid offer only /looks/ cheap, until you see what we charge you for consumables!"
It seems like a fairly recent shift -- heck, the whole solar generator concept is a fairly recent shift -- but maybe it's an indication that LiFePO4 devices are becoming more common in the consumer space.
It has other tradeoffs, though, like being physically large compared to a lead-acid battery of similar capacity (or, say, a bunch of 18650s).
And like other Lithium-based cells, longevity is maximized by never charging it to 100% and leaving it there long-term -- which, unfortunately, is probably not what Ecoflow is doing. (Ideal long-term state-of-charge is closer to somewhere between 50 and 80%.)
Things may have changed, the APC UPS systems I've used required you to power off to replace the batteries. the CyberPower units I've used allow for replacing the batteries hot.
I've had terrible results with Tripp Lite UPS systems - where they fail for no reason at all, and will not auto power up after a power failure.
At a very large size of 30KVA, I've used Eaton UPS systems and they have been rock solid.
In the winter months (when we have most of our power outages), I pay for a pre-paid cellular SIM for backup. The cell tower(s) that serves my area must be on generator, it doesn't seem to go down even in long power outages.
I guess you could have a bad cable where the CC wire has broken and can't do USB-PD.
Their customer service is supposed to be legendary. If you drop them a (polite) descriptive note, signed with your name and address, I'll bet you a beer that you'll have a new cable in your hands by the middle of next week.
The only advantage to buying new is weight. Newer UPSes tend to be a lot lighter, but that's often because they cut corners on the magnetics and/or use expensive, hard-to-replace lithium batteries. Weight is a high priority for the manufacturer to optimize, but not for the consumer. When it comes to UPSes, old school big-iron transformers and heavy-metal batteries are the way to go IMO.