[Samsung Galaxy S21 Ultra] kmdigital:
Last night I broke down and flashed it with the U1 XAA firmware, using the CSC (not Home) file. It went well, finishing the flash in <4 minutes. Then spent the next 4+ hours reconfiguring things that aren't automatically restored by using SmartSwitch to restore. I'm not sure how that works, but it seems that it doesn't actually back up the apps, rather it just backs up the name and placeholder, so when it's restored it has to redownload every single stinking app again. Plus, I had to go through and relog into every app where this is an issue, plus because it's now called SM-G998U1, I had to delete all the old G998U devices in various places, particularly Google. What a pain... Kind of wish I'd tried the Home CSC, particularly after what I see below.

What's interesting is that I know have the N2, N5, N66, plus the N77 and N78 C-bands, (as well as N260) but I lost the T-Mobile specific bands of N41 & N71, in addition, I also lost N261. I don't care about these as I'm not in an area where the Ka millimeter wave bands matter. However, I do find it interesting that the U1 firmware removed the TMB specific 5g bands. I would have thought that the Factory U1 firmware would automatically support all US carrier bands, but I guess not.

I'm using Visible (Verizon MVNO), and while it worked "decently" before, it's now orders of magnitude better than it was previously as a U device. I debated installing the VZW firmware, but decided not to, and I most definitely don't want to go through setting everything up again. However, I know have a MUCH better signal at my house, a consistent 5 bars, and a signal right around a 89-90 dB, while previously it hovered around 105-109 dB, which is pretty marginal, particularly when the antenna is only about 1/3 mile away. It also now tells me that I'm on LTE+ (rather than LTE 4g like before), so apparently this particularly tower isn't 5g yet, and I haven't left the house yet to see what I get at other locations from other towers.

However, what's really astounding is the speeds that I know get. Previously, download speeds would always start off slow at around 10 - 15 Mbs, and eventually get up to around 60 - 70 on the average, with upload speeds typically maxing out around 15 Mbs. However, now, I'm getting consistent download speeds of right at 240 Mbs (Visible limits max speed to around 250 Mbs on 5g), and upload speeds of ~70 Mbs. It's an incredible difference, so my suspicion is that I may be getting some 5g speeds, even though both Network Cell Info and LTE Discovery apps tell me that I'm generally only connected to the B2 and B5 LTE bands. Or maybe it's possible to get that kinds of speeds out of LTE with the new technology (forget what it's called) that shares bands at the same time, hence the LTE+ moniker.

Also, even though I installed the CSC file, the Service Provider Software is still ATT/TMB. To be specific, it's SAOMC_SM-G998U1_OYM_ATT_12_0026 ATT/ATT,ATT/TMB, and there isn't VZW anywhere. Maybe this will eventually update I don't know. However, it did remove the ATT startup splash screen that I had previously, so that's changed.

It also automatically downloaded and installed One UI 4.1 afterwards, so that seems to be working properly. Any thoughts on any of the above?

Thanks for the help that was provided previously.