Ultra Low Latency mode prefer used ipv6 server not ipv4 server

According to this post described, I had  regenerated/reinstalled the Apple profile.  I got the Ultra Low Latency mode and used the  ipv4 server ( estnoc-tpe ) under mobile network ( ipv6 enabled ). However, once I connected to WIFI  ( with ipv6 enabled ), NextDNS will prefer to use  ipv6 server in Ultra Low Latency mode. However, NextDNS does not provide ipv6 server in Taiwan ( estnoc-tpe ),  so I was forced to connect to the Hong Kong sever ( anexia-hkg  ) . Even when I used the mobile network ( ipv6 enabled ),  it connected to the Hong Kong sever, too.  Reboot cellphone will return to the ipv4 server. But the same thing was happened, when I connected to WIFI  ( with ipv6 enabled ). I do not  want to use the NextDNS official app ( VPN mode ).

My question is that if is possible to use ipv4 server first under Ultra Low Latency mode? Especially in  the NextDNS do not provide ipv6 server region, thank you!