Perhaps this is interesting for you…
https://discourse.coreelec.org/t/wireguard-client-not-connected-when-allowedips-0-0-0-0-0/18187/5
I still use Wireguard from Entware with CoreELEC (21.0, ng; S905X3).
For Wireguard CoreELEC clients:
AllowedIPs = 0.0.0.0/0
Does NOT work
But (in my case):
AllowedIPs = 10.1.1.0/24
works perfectly. I use this to connect WG CoreELEC clients as tvheadend clients with a WG CoreELEC server as tvheadend server, too.
For other OS clients (Windows, Linux, Android; NOT CoreELEC):
AllowedIPs = 0.0.0.0/0
is OK.
You can use this tool:
https://www.wireguardconfig.com/
to generate server / clients configs.
In WG CoreELEC clients configs you should change:
AllowedIPs = 0.0.0.0/0
with:
AllowedIPs = 10.1.1.0/24
(this is an example; only the WG subnet)
Kind regards