For the smart switch thing, I think you're looking at the wrong place.
As in, where the downgrade button is, it doesn't say if your software is up to date or not.
The process should be. Open smart switch, connect phone physically, allow permission on phone so it properly connects. Give it maybe 10 seconds, at the bottom of the screen where the backup button is (on the pc) there should be a downgrade button. There have been reports of it missing. If it never shows up for you, there is a nuclear option.
The nuclear option. Basically, samsung phones have a system where a pc can reinstall android onto them. In the event a phone is fully bricked, it can be fixed. In your case, it means you should be able to reinstall the latest version of android, being one ui 8 stable. This will wipe all data so do a smart switch backup first.
Now, shut the phone down, connect it to your pc via a cable, hold volume up and volume down together for a while. You should after a few seconds see a very blue/teal screen. Press volume up to enter the full thing (I think, follow what it tells you on screen). Now open smart switch on that pc, press the 3 dots top right, press emergency software recovery. Your phone should appear in the list, follow on screen instructions and hopefully it should flash stable one ui 8 to your phone
