I'm actually tempted to give this a go, I just wish I had the funds to afford it right now. Even at around £400, it would absolutely obliterate the bank. However, it actually represents pretty good value when compared to offerings from Huawei and how much they're selling for - the unbranded H122-373 is often selling for at least £250, but more like £350-400 for new condition. Don't bother with the Three-branded H122-373, since they're still technically Three property and anyone selling them technically needs to return them after the contract is finished and the device will still be tied to their account (I mean, you can still use it, but Three will never unlock it, and you will never technically own it).
On 5G on 3, the Huawei H122-373 gave an average of about 170/10 Mbps throughout the day. Early hours in the morning, this could reach over 300 Mbps on the downstream, usually sitting around 250 Mbps. Safe to say, speeds usually sat in the 100-200 Mbps bound most of the time it's in use. Due to the nature of that hardware, I couldn't see the exact bands in CA, but I would wager 1-3-20_n78 for DL.
The reason why this would nice to try out is because it actually has external antenna ports, so I could find a better location to improve the upstream. Around 10 Mbps upstream is ... pretty poor. The B525 with external antennas could perform better, so clearly using a unit with only internal antennas is not favourable for my location.