Temporarily disable the HSTS security feature.

This is not possible in current versions of Chrome, Chromium or Edge, but it IS possible in Firefox:

1. Downloand, install and run Firefox
2. Type in address bar: about:config
3. Select "Accept the risks"
4. Find "network.stricttransportsecurity.preloadlist"
5. Change "True" to "False".
6. Restart Firefox (may not be necessary)
7. Now you should be able to use Firefox to access http://www.mywifiext.net as intended. (If it doesn't work, double check so that you are not trying to go to "https://..."
8. Once you are done, recommend repeating the steps (set it back to True) to keep your system as secure as possible.

Temporarily disable the HSTS security feature.

This is not possible in current versions of Chrome, Chromium or Edge, but it IS possible in Firefox:

1. Downloand, install and run Firefox
2. Type in address bar: about:config
3. Select "Accept the risks"
4. Find "network.stricttransportsecurity.preloadlist"
5. Change "True" to "False".
6. Restart Firefox (may not be necessary)
7. Now you should be able to use Firefox to access http://www.mywifiext.net as intended. (If it doesn't work, double check so that you are not trying to go to "https://..."
8. Once you are done, recommend repeating the steps (set it back to True) to keep your system as secure as possible.

(Another similar solution is to find any other browser that does not implement HSTS or allows to disable it.)