[Samsung Galaxy S9+ Questions & Answers] Freshwave@gmail:
Last week on Thursday, I allowed Verizon to install their Software Update 21 (April 2020.) It made it as far as the going through the optimizing apps and then was stuck in a boot loop. The phone would be usable for about a minute, then would freeze, and then reboot. If I clicked on the System Update option in settings, it would say that a system update was in progress. I chatted with Verizon, and they ended up telling me that the only way to stop the update was to do a factory reset, which I am doing everything I can not to do that as I don't want to lose my data.

I changed it into maximum power mode and it did stop the update for that time being and I was able to use the phone, texting, etc. This allowed me to at least connect the phone to my computer to backup all of the directories. After many reboots, on Friday it finally stopped doing the update and gave me an error which I think was 410. It thought it was updated, though did show as failed. When checking for updates, it said it was the current version. Twice I was able to get the phone to stop by freezing when going to the app and stopping some programs (sadly, I was not able to remember the exact combination that worked) which allowed me to use the phone like normal. All this while, I was uninstalling a large amount of the apps that I had installed hoping that would minimize whatever may have been causing the problem.

Went to each of the google and samsung apps, stopped, disable, and reverted them all back to factory defaults. Guess that was a bad idea, from then on I received an error as soon as the phone started which caused it to go directly into recovery mode. I chatted with samsung and they thought it might be a hardware issue. I still think it is related to their software update, so not a hardware issue.

By using Odin, I loaded the firmware from March 2020, and when it rebooted, it did go as far as optimizing the apps, though anytime it booted up, it would never get past the white verizon loading screen. It took me hours before I discovered that Odin was failing to load the firmware on the phone as the Windows 10 laptop only had USB 3.0 ports which don't always work with Odin, and ended up being successful using my old Windows XP laptop as the USB 2.0 ports worked fine. After a bit hanging on the verizon loading screen, it would reboot and never went past. I have been able to load the March and April 2020, though none of them will ever get past that white verizon loading screen. I did see something say that in loading TWRP, I could possibly do a full backup of the phone which is what I would like to do.

One time I only loaded the AB file for a different version than I had loaded, and it was the first time it went beyond the white screen, only to tell me that the verification failed and it would need for me to do a factory reset. I was able to reboot the phone without actually doing the reset.

I have read many posts here and the forums on androidcentral, and with so many things, I really needed to post to get guidance from people here that can point me in the right direction for any other things that I can try. As you have read, doing everything that I can to get the phone working by keeping my data. Any help would really be appreciated.