This isn't a power bank, but the EcoFlow River makes for a great mobile battery pack for many uses (like camping, road trips, etc) but also qualifies for a UPS (which means it has to be able to switch over to battery power with certain milliseconds.. that part i'm not sure, but the professional UPSs switch over in < 10ms. I think EcoFlow is < 30ms but I'm not 100% sure).

I've had the River Pro for a few months and it's worked perfectly for that use case. And UnRaid supports it as of a couple months ago.