I have checked add-ons, apps, it seems there is nothing blocking. Plugin Manager is marked as Incompatible, but this is probably "normal". And there is no Disable button for it. There is also a bunch of localizations with Unknown status. Can be disabled.
Postgre 9.5.15 still supported.
Need to check Xmx and other values, they should still work, but it is better to set them higher as per document.
First startup should be longer because of new indexing tables.
After the upgrade i suggest enabling bulk email notifications: Cog > System > Batching email notifications.
Initial upgrade completed
I have enabled Batch email notifications. Will see how it goes. Closing this issue.