@David-TP 

Hi David, 

Like many in UK options are limited due to British Telecom Openreach, the line has been faulty for 20 years but they won't fix it & I'm in a city, I've been using 3G then 4G since mid 2000's. 
 

However I need a back up incase the 4/5G network goes down and the secondary kicks in, so I'm guessing without a external router I can't use two X50-5G in this manner?. 
 

Quite limiting given there isn't a dual sim 5G TPlink option on the market and 4G backup is restricted to Class 6 LTE when 4G is so oversaturated especially since 2/3G are shut down ans all calls/data are being VoLTE router en mass these days.
 

Well obviously TPL management don't realky understand mobile networks other than minimum 4G and a 5G will "do fine" severely limiting future compatibility & non compatible with each other in the basic OS engineering knowing dual sim aren't available so this should be a option for two TPL devices, esp at least 5G products.