I just did this last weekend.  It went fine on our end.  I turned off the alerter in config.php first, upgraded, then followed the install guide to ensure that everything was properly installed. Naturally PHP 7.2 was not and running the apt line in the install guide fixed that.  I was back running again quickly.  That said, I was setup using mysql so I wasn’t affected by version updates.

If you have rancid bolted on, you might consider doing a rancid run and checking the log. I found errors which had to be fixed which I strongly suspect were pre-existing.