I noticed some slowness but not directly from the router or atleast I think.

My modem is a AX6S with openwrt 22.3, but it was still pushing a ula prefix and wan ipv6 address.

When I investigated this further inside the slate ax, I had one wireguard client instance active with mullvad and to my surprise it was pulling a ipv6 address even though I had the full ipv6 off for this router but ipv6 delegation was not off in my wireguard device.

Especially since my modem uses cake sqm, as soon it uses anything with ipv6 I get severly slowed down, I saw speed like 60mb/s download and 100mb/s upload when I should get 200 mb down and 200mb up as advertised speeds, that was quite strange behaviour.