Is it a good bad idea to do a inline upgrade of the server?
If yes (I guess) how can I migrate all data from one server to the next? I really do not want to recreate all jobs, export and import backups and so on...
Not a bad idea at all, just backup Veeam B&R configuration prior to the upgrade, so in case if something goes wrong, you could restore everything back. The same functionality can be also used if you need to migrate to another server.
I have done that and it was painless, everything seems to work fine.
The only thing I am missing is the "search" icon on the start screen next to my user. With every 2012 R2 server I installed from scratch I have the search and power icon next to my user. After the in.place upgrade this is missing and I do not find how to get it (personalize and tiles do not offer that). Maybe you have any idea, even if it's not veeam related ?