No, it's not an icon problem. I tried many speedtest and speed is really low. With stock global rom and 4g+ speed is really faster.
You can see that with .eu rom sometimes the icon appears and then disappears, so the icon has not problems.
It's a big problem and for this it's impossible to use this .eu rom now. Seems like an aggregation bands problem.
There is this guide, but it's only for 855 processor:
https://forum.xda-developers.com/Mi-9/how-to/enable-4g-4-5g-carrier-aggregation-mi9-t3977213
We need a fix asap