OpenWRT - How to redirect all subdomains of a hostname, to the same host, so that it can be reverse proxied?

I sorted it out eventually.

According to:

https://openwrt.org/docs/guide-user/base-system/dhcp_configuration#a_and_aaaa_rr

Which states:

This is an implementation of the --address option. Return 10.10.10.1 on query domain home and subdomain *.home.

I was able to login to OpenWRT (using ssh [email protected]), and running:

uci add_list dhcp.@dnsmasq[0].address="/server.local/192.168.1.200"
uci commit dhcp
/etc/init.d/dnsmasq restart

Which then allows the following to work:

~$ ping www.server.local

PING www.server.local (192.168.1.200) 56(84) bytes of data.
64 bytes from server.local (192.168.1.200): icmp_seq=1 ttl=63 time=55.4 ms
64 bytes from server.local (192.168.1.200): icmp_seq=2 ttl=63 time=77.3 ms

And anything else for that matter:

~$ ping hdsjdjk.server.local

PING hdsjdjk.server.local (192.168.1.200) 56(84) bytes of data.
64 bytes from server.local (192.168.1.200): icmp_seq=1 ttl=63 time=101 ms
64 bytes from server.local (192.168.1.200): icmp_seq=2 ttl=63 time=124 ms

As I understand it, this creates an A record in DNSMasq, which automatically includes all subdomains.

The changes can be seen in /etc/config/dhcp, which now looks (partially) like:

config dnsmasq
        [...]
        option domain 'local'
        option local '/local/'
        list address '/server.local/192.168.1.200'

[...]

Hopefully this helps someone else in the future!