So my 5G UC seemed very slow to load any pages in any apps. I ran speed tests and was getting great speed results. However, using apps didn't match the reported speeds that I should be getting. If that seems the case for you then this should fix it.
Go into device settings. Then connections. Then SIM card manager. Turn off your active SIM and wait about 10 seconds. Turn that SIM back on.
Now your device should actually pull those speed test speeds in all your apps.