Mikrotik (at now…) doesn’t sell cheap and outside 5G routers. I don’t like consumer 5G routers (eg. Zyxel, ZTE, etc.) because they are not manageable and monitorable as Mikrotik ones, so I decided to assemble my own and custom one from scratch! I used a RouterBoard RBM33G, a Quectel RG502Q-GL (you can find on budget on chinese marketplaces websites…), an USB3 to M.2 adapter I found on Amazon and it already have also pigtails and RPSMA connectors. I used also two omnidirectional diversity antennas (they’re cheap, compared to panel antennas). I would have preferred to use a miniPCIe to M.2 adapter, but USB3 miniPCIe to M.2 adapter are at most unobtainable, expensive and more than anything else it cannot be used on RouterBoards because they don’t have USB3 on miniPCIe 
So you’d be “castrated” to USB2 speed (and max 220~250Mbps DL/UL speed).
On Github I explained the reason I did it. My router is completed and ready to be mounted externally, I’m waiting for the DeNAT SIM. This project is a WIP, I already tested the router with a temporary SIM, but I’ll add speedtest and other info when it will be mounted and with the final SIM.