at the bottom of the screen in samsung members you'll see the different page options in my screenshot below. you want to select support on the far right then once on the support page scroll down to find quick help and select feedback. when you open feedback your logs will begin being sent. it is very important to send your logs via that feedback option within 15 minutes of the error that occured. you'll want to keep samsung members open until you receive the notification that the log submission was completed before closing the app. it can take several minutes for your logs to be sent to the backend team as well so don't panic if it feels like its taking forever 🙂 Its always a good idea to include any screenshots and a detailed description of what happened when any error happened on your end. that also helps samsungs teams to narrow down the issue to fix it. 
since this all happened and your device didnt reboot on its own, have you restarted your device? I saw where you said you had already ran the diagnostics on your device and nothing was showing any errors or that they weren't working at that time. However with the S pen now not working see if you can run the diag on just the s pen. To run just the one test when you go to diagnostics and it begins all of them tap back one to bring up the full menu of tests and just select the S pen. This is quite the pickle you have going on with different functions simultaneously not working.
Another thing to check is both google play and the galaxy store to insure you don't have any other updates that didn't complete on their own once you updated to One UI 9. Lastly in your settings menu go to your google services. once on google services scroll down until you see system services and select that option. If you see any updates in system services that need to be completed go ahead and push those through as well. sometimes not everything gets with the program accordingly. I've included a screenshot for reference of what you'll be looking at in system services.
Restart your device once you complete any remaining updates if it does not automatically prompt you to do that.
Another thing to check is both google play and the galaxy store to insure you don't have any other updates that didn't complete on their own once you updated to One UI 9. Lastly in your settings menu go to your google services. once on google services scroll down until you see system services and select that option. If you see any updates in system services that need to be completed go ahead and push those through as well. sometimes not everything gets with the program accordingly. I've included a screenshot for reference of what you'll be looking at in system services.
Restart your device once you complete any remaining updates if it does not automatically prompt you to do that.
