Yesterday (early August 2021) my Ubuntu 20.04 installation started configuring all network interfaces (wifi, ethernet) with IPv4 addresses from the wrong network segment block, namely 192.168.0.x. IPv6 still worked fine.
I didn’t figure out whether that’s due to a change in the router or the OS (I suspect the router, because the situation improved when increasing the DHCP lease time ), this solution however  works for me.
must be reconfigured, in my case
network: renderer: networkd version: 2 ethernets: enp5s0: dhcp4: true dhcp-identifier: mac wlp6s0: dhcp4: true dhcp-identifier: mac
 networking – Wrong IP address from DHCP client on Ubuntu 18.04
 What is a good DHCP lease time?