im having the same error as this guy but on an actual wii. ive tried setting the dns to the new wiimmfi dns, setting the wii as a dmz, port forwarding; nothing works at all, i keep getting the same error.

Well then it's probably some oddity in the college network. Unlikely that you'll be able to fix that without having access to the router to reconfigure it. 86030 means the game was unable to get a DNS response (get the IP) for the Natneg server.

I downloaded mkw-wiimmfi-patcher-v6 and successfully created a modified copy of my Mario Kart WII game (RMCP01).
When I connect to WIIMMFI it makes me do the procedure to choose the character, the machine, automatic or manual and then search for opponents in the world crashes after a short time with ERROR 86030.
Search for opponents in the region remains in search for a long time without result and sometimes after many minutes it crashes with same error above.
1-I tried to put google DNS to no avail.
2-I tried to put static IP and on DMZ WAN router set with the same IP but nothing changes
3-I tried to set WIIMMFI.DE (46.4.79.141) (95.217.77.151) as DNS ip without result.
I tried to get other custom versions MarioKartCris3.5CT [RMCE86] and Wiimms MKW-Fun 2020-02.v2.pal [RMCP43], in these versions the search in the region continues for a long time without any response.
I noticed that I can still download Ghost Race without problems in all versions, so for me it connects ...
I am a beginner in the field, can any expert help me?
With traditional Mario Kart Wii (RMCP01) should I find someone in the world who plays or should I have a friends list?
Please a little help ..

Sometimes I can join in World races of Mario Kart Wii, so last two days we have tried to play Wiimms Mario Kart Fun 2020-02 (RMCE43). We got the screen with searching for the opponents, but without any luck. I think, that the problem is we don't have players of this version.