I've noticed that the example page with a mapframe [1] doesn't show the frame on the mobile website [2] or the Android app or the iOS app.
For the mobile website I was able to see that the issue is that the request to `maps.wikimedia.org` returns a 400 Bad Request.
This is the request done on the desktop website that works fine:
```
https://maps.wikimedia.org/img/osm-intl,14,-33.92151,18.4213328,400x250.png?lang=en&domain=en.wikipedia.org&title=User%3AJMatazzoni+%28WMF%29%2Fmaptest&groups=_cfd0a90b704aff0ccc1e22cc6f3d7b05a1075ea1
```
While the mobile website uses a different group ID, while keeping the same domain `en.wikipedia.org`:
```
https://maps.wikimedia.org/img/osm-intl,14,-33.92151,18.4213328,400x250.png?lang=en&domain=en.wikipedia.org&title=User%3AJMatazzoni+%28WMF%29%2Fmaptest&groups=_23d973ffe007348f605b87c5808ecf9ed87356f9
```
That results in a 400 with body:
```
"GroupId not available"
```
[1] https://en.wikipedia.org/wiki/User:JMatazzoni_(WMF)/maptest
[2] https://en.m.wikipedia.org/wiki/User:JMatazzoni_(WMF)/maptest
NOTE: I added a map on the above test page that does NOT have a fancy link with a marker. Interestingly, that map DOES render on mobile web site, but not on ios. (the fancy map renders on neither).