Here it is:
I suspect that a failure of the disk or the SATA <=> USB3 box was the problem.
This resulted in the Raspberry Pi-4 running amok and after a number of hours brought down my entire network.
When I got home the wifi, switches, nothing was working.
So I checked the disk with my laptop.
I decided to put a new image on it.
I use the Balena Etcher, but the second pass it stopped at 43%.
So I found in my closet a brand new disk and SATA <=> USB3 box.
Now it was possible to flash in less than 30 seconds!
Now it is the case that starting with version 2023.6, you can add a backup directly, without having to make any initial configurations!
It’s really cool!
So I plugged the disk into my PI-4 and booted it up.
I couldn’t see anything in browser, but that was because I was using a different port, not 8123…
But then I brought up HA, it said it could take up to 20 minutes before it was done.
Then it appeared, the login.
At the bottom there is an option to restore/load backup directly.
I had previously drained my backup from google drive.
Pointed it out and now HA showed that it loaded on the backup.
In another girl I entered the address again, but no answer, I was on port 8123, not the one I have entered in HA and which is saved in my backup.
I had to wait a good while and suddenly I was logged in.
Now it was just a matter of restarting the ENTIRE Pi-4
It took an unusually long time before HA was up and running again.
But on the whole, I think it seems faster, even with external access!
A very good link is Home Assistant: Ultimate Restore Guide