How do you set the search domain? GL-MT3000, firmware 4.11.0

Router VPN, DNS, Leaks
1

I have a GL-MT3000 running firmware 4.11.0.

I have a WireGuard config that has something like:

[Interface]
PrivateKey=<PRIVATE_KEY>
Address = 10.0.10.4/24, fd10:0:10::4/64
DNS = 10.20.1.1, myhome.lan
...

While the interface can be brought up, the search domain is not being set to "myhome.lan".

How do you set the search domain for a wireguard tunnel (please explain it in "networking noob terms").