These entries are generated by the new part of the unbound-dhcp-leases-bridge, the unbound-dhcp-leases-client.
The …-bridge registers (name, IP) tupels to unbound, the DNS server. The …-client is called from the DHCP server, when new leases are generated, and sends the information to the …-bridge.
This functionality is new to IPFire and I suppose these log entries will disappear in case of proof of functioning with one of the next CUs.
Thanks for clarifying, I was guessing in this direction. But I think it’s a bit strange why this began to appear not directly after the core upgrade but two weeks later.