Look on AliExpress for the generic "LTE/5G" routers that have or can add a modem to. ~$250
Probably good idea to drill a couple of extra holes into the back to the additional antennas for the WWAN to pick up / bond additional bands and add pigtails/antennas as needed. IIRC they usually only have 2 antennas for the WWAN but modern modems have 4 antenna ports on them.
While it's not a hotspot in the traditional sense it's goin to be more robust than the little boxes you usually see. I'm not sure why they say 30/60/100 users but, it's either limited in the DHCP setup they se ton their boxes or limitation invoked somewhere else in their config. The biggest issue with a WWAN would be saturation of the connection depending on which service you end up connecting to. Time of day makes a difference as well for how much bandwidth you would get vs saturation of the cell site.
If you want to save money on the SIM/monthlies cirlcedin.com has discounted full phone plans with unlimited data for each carrier. I've got a TMO one w/ unlimited 5G + 40GB hotspot for under $40/mo. I use it as my primary connection and usually run anywhere from 700GB-1TB each month through it. 50% the cost of cable and it works anywhere I go.. Baseline for me is 200/30 when moving around but, if I pop the sim into my phone it's hit 600/100. There are times though in the home it hits 300-400 / 100 which isn't bad considering the cost.
You'll likely need to swap the IMEI / TTL values though using it in a router and more info on that can be found @
https://wirelessjoint.com/
My setup I have the modem in a USB "dock" and run it off my linux server which is my "router" and it doesn't need the TTL tweak to avoid data bucket being used. I picked up a cheap 2nd modem though as a backup and it only works in PCIE/NDIS mode and does deduct from the HS bucket which is similar to the "router" option.
I went with a SIMCOM modem as my primary and Fibocom as my backup. There's only a handful of choices out there though for brands but each have a bunch of options depending on the speed / tech requirements you might have. 4G is going to be barebones connectivity across carriers with dismal sub 50mbps speeds in most cases. 5G though is where the bandwidth is. SA/NSA seem to both work about the same as more SA sites get turned up. When I first started playing around though the SA didn't offer much for speed <50mbps but, they tweaked things and now it performs the same as NSA but lately SA hasn't been an option which means they're still working on it.