I'm running OpenWrt SNAPSHOT r13649-b1d5ab1a69 on a Linksys WRT-3200ACM. I've got Wireguard configured to connect to Cloudflare Warp. IPv4 works. IPv6 doesn't - LAN clients cannot connect to ipv6.google.com, for example. On the router I can ping6 the Warp peer, but not other IPv6 addresses.
Wireguard config from /etc/config/network:
config interface 'wg0'
option proto 'wireguard'
option private_key 'X'
list addresses '192.168.11.2/32'
list addresses 'fd03:2319:63b0:a80b::2/128'
config wireguard_wg0
option description 'Cloudflare'
option public_key 'bmXOC+F1FxEMF9dyiK2H5/1SUtzH0JuVo51h2wPfgyo='
list allowed_ips '0.0.0.0/0'
list allowed_ips '::/0'
option route_allowed_ips '1'
option endpoint_host '2606:4700:d0::a29f:c001'
option endpoint_port '2408'
option persistent_keepalive '25'
Relevant portion of /etc/config/firewall:
config zone
option name 'Warp'
option input 'REJECT'
option output 'ACCEPT'
option forward 'REJECT'
option network 'wg0'
option mtu_fix '1'
option masq '1'
config forwarding
option src 'lan'
option dest 'Warp'