Thank you very much for your reply. I have done updates from Win7 to Win10 in the past without any problem (with backup always in hand). However, the upgraded systems at that time did not have any bypass installed. Therefore, the aim of my question was to find out whether Win7 BypassESU causes problems to the upgrade process, and, possibly, how to avoid them.
Upgrade should still be possible (maybe to an older version of 10 first), however, it does not grant you a free license anymore. That ship has sailed.