Ok, yet strange indeed! On the old Arduino IDE it still shows the "port" option but greyed out, even if it cannot find any available ports.
Thats why I said it helps showing that the hardware is functioning even before compiling and uploading attempts.
For example in this my case the Uno is programmed direct via ISP mode using a Pickit4 and it must be considered that the Uno does not have to be plugged in as the Pickit4 could have supplied the target voltage directly.
Is this problem specific to minicore? If I flash back the arduino standard core would it make any difference?