Everything was described in the thread body message or in the comments. Qubes 4.3 was installed with external boot partition with the method described in this thread by @apparatus and improved by @ merowing. I don’t use Fedora so system qubes are Debian 13 based. I connect the stick to the usb port that is assigned to the disposable sys-usb that is offline qube and has “provides network” option disabled. Normally the stick should appear there in devices list in hilink mode (as network device). Then I attach it to the sys-net (which is persistent). It appears there as ethernet connection which I turn on and start Tor connection.
This worked like this in Qubes 4.2 (which was with external boot partition too) but after fresh installation of Qubes 4.3 this all immediatelly started.
Fresh installed Qubes 4.3 has only one kernel: 6.12.59-1.fc41. I deliberately didn’t update dom0 so that Qubes wouldn’t switch to a different kernel and make changes that would cause this issue.
For the most complete information about the history of all the actions I took over the past two months, you can reread the entire thread.