The system map is not working, I tried all the different combinations such as
serveripaddres:8888/index.html.
:(

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the link should be localhost:8888 for fabric and localhost:8888/index.html
There's a tutorial video by @jonafanho that tells you how to do it here: https://youtu.be/_qTHwkjQwNQ?t=440

Is your world open? There could be a bunch of reasons why you can't load it.

Likely the computer hosting the server has not forwarded port 8888

What OS are you using?

There are specific ways to see if ports are opened or not

I'm playing on a server that is hosted by pebblehost,
Windows 11 as an OS
and the world is open...
also I tried all different combinations :/

Server hosted by third-party partners may not open the specified port. You can contact to you hosting partners to get more solution about make a NAT with other ports, like dynamic maps.