Looking further into these, it seems they often won’t work in a computer UPS due to current limitations. Most are rated 10A continuous which translates to 240w in a UPS with two battery units. Adjust for conversion losses and I’d estimate any load over ~200-210w would shut down the batteries (via their internal BMS).
I reckon for a light load (basic desktop; no GPU; one display panel) they’d work. My dual-GPU desktop idles at 100w (stupid Mellanox) and the four display panels draw another ~110w combined. That’d leave zero headroom.
I discovered this after a pair of original equipment batteries failed and I went down the “what should I buy” rabbit hole. So I grabbed a pair of ExpertPower from Amazon. I figure “ships from and sold by Amazon” along with these being a best seller ought to be good enough for my non-critical setup.
It seems PowerSonic, CSB, Yuasa, and EnerSys (Genesis) are the recommended vendors for mission-critical apps.