Starting from 10(or9) debians, I observe the problem of the work of isc-dhcp-server, if it is on a virtual machine.
I have clean default install of proxmox7 and debian 11 with isc-dhcp-server on VM. No vlans, all simply.
No apparmor,selinux of firewall (nft iptables etc on the vm)
Tcpdump on...