Our routes always use IPv6 first. Lately, IPv4 addresses of servers abroad have been restricted from China much more often than IPv6 ones, so every route’s default entrance is on IPv6, with IPv4 kept only as a backup. If everything works on 4G/5G mobile data but no host shows a latency number as soon as you join a particular Wi‑Fi network, that Wi‑Fi usually has no IPv6: please turn on IPv6 in your router. Normally, leave your app on “自动选择”. On a network without IPv6, it switches to “IPv4 备用” (IPv4 backup) on its own. Back on a network with IPv6, Clash Verge Rev and FlClash switch back by themselves; with sing-box, disconnect and reconnect once.