shadowsports, thank you for your reply.
I did not change anything to my computer for more than 6 months. Anyway, I managed to solve this by going into Settings > Update & Security > Activation and there was a 'troubleshoot' button. I clicked on it and in 3-5 seconds the Windows got activated back with 'digital license'. I initially searched the error code (which I do not recall) on Google and found a lot of people complaining in the past, etc. - but yey, it was easy this time. When I said "'GG' from Gigabyte" I was ironic, suggesting that things that were not meant to change were changed in the new BIOS.
Related to unkown device, I searched some hardware ID's and found some results talking about Thunderbolt. Then I went into the BIOS to see that all the previous settings have been reset to default, hence activating the Thunderbolt that I do not need / did not install previously. Disabled that again and now it disappeared from Device Manager. So thank you for the suggestion.
Just as a side note, I find the new BIOS design dreadful. It looks like some kids draw it and the colours / shadows seem from 15 years ago. The previous one was much, much cleaner, the fonts more readable, the colours more adequate, etc. - now I do not understand why I had to update my BIOS, lol.
Anyway, thank you for your help.
