If you're buying a 5G router off eBay, Amazon etc, beware. There are a lot of ads claiming routers are 5G when they're not. (As a rule of thumb, any routers under £100 which look pocket sized are probably not 5G.)
Also, many routers for sale are tied to a particular network (3, EE etc). If you need one that you can use on any network, make sure it says "unlocked". At least if it states this in the advert, you should be able to get a refund if it turns out not to be.
The following are confirmed genuine 5G makes/models. (I'll add to the list as and when.)
ZTE MC801A
Huawei H112-370 / H112-372
Zyxel NR5103 / NR5103E
