It seems I found the reason why it happens. I watched the log and there is a white paragraph that is repeated several times, saying that it can't set template to non-existing qube default-dvm-Fedora-43. And another message is repeated the same amount of times, saying that qubesd can’t start and its start is sheduled for a certain period of time later. The rest of the messages are literally repeats of yesterday’s messages.
It is possible that because of some reason qubesd tries to set a template to the Fedora based default-dvm that is deleted now. Gets an error and shuts down. The thing is that I created Fedora based system qubes to check if the stick will work better with Fedora based sys-usb. When it produced the opposite result I deleted all Fedora based qubes, including Fedora based default-dvm. There left only Fedora template. But I checked everything before deletion. In Global Configs I set Debian based disposable template as default-dvm. And all system qubes were set back to Debian based. Their autostart was ebabled too. Also checked if every disposable qube has Debian dvm as its disposable template. So I have no idea why qubesd tries to set template to the deleted qube.
Will post that message picture a little later.
And most important: what to do now? Qubesd doesn’t work so I can’t execute any command based on it. How can I force it not to set the template to the non-existing qube?