Sunday 24 november at 6.24 am (Rome timezone) multiple raspberry pi 3 model b (and raspberry pi 4 too)with raspbian buster installed and dhcp configured on the lan are gone offline at the same minute then they stopped to works forever on lan and still works on wifi instead.
It is not a hardware issue, because if I change the microsd with a fresh raspbian it works well.
I made a scan with clamav and I found nothing sospicious.
The devices was all configured withotu a firewall installed, without fail2ban and user PI and a password mediam safe and one of them with a high secure password..
All with the door ssh 22 opened, and sudo not forced to ask for the password.
What could I do to discover from where this issue came from?