"ssh-ed25519 host key mismatch for openwrt.lan !"

Installing and Using OpenWrt
2

Usually the client tells you, odd:

ssh-keygen -f "/home/<foo>/.ssh/known_hosts" -R "192.168.1.1"

Thats the command on Debian-based distros.

It should. It resolves to get the IP.

Verify nslookup openwrt.lan resolves to 192.168.1.1.