@coffeeandspice
I was also seeing some slowness on Plesk Obsidian, increasing the timeout helped there. It’s indeed possible to refresh the page when you’re doing the UI upgrade to continue the process where it stalled, so I think your database should be OK.
We did see a similar warning about LazyCollection in this topic: Mautic 3.0 Installation Error - Row size too large
You seem to be using the correct PHP and MySQL versions, so that looks good to me. Saw a similar error in https://github.com/tightenco/collect/issues/181 but there the user was running the wrong PHP version.
At this point I’m not sure what is causing this warning to show up for you. Could you maybe, just to be sure, remove your cache folder and try again? Does that make any difference?