The map scale gets hidden on the left the French Wikipedia because it overflows.

Here's what it looks like:
(example URL)

Here you can clearly see the overflow:

But there's no problem on Wikivoyage:
(example URL)

All is needed is to add

.leaflet-right.leaflet-bottom {
    max-width: 100%;
}

Result:

Wikivoyage added it to its own installation, but it would be better to fix it globally than to just add it to the French Wikipedia.
Can someone make a patch for it?

Here's where the code needs to go:
https://phabricator.wikimedia.org/diffusion/EKAR/browse/HEAD/styles/control-scale.less;af8f70d386f93c7d2057ec57a341aaf33e8263f6$11