Litalino just to not confuse anything:
A slug driver in Flarum is a special mechanism that automatically generates a URL for a given resource and where the actor has no opportunity for customization. Discussions use a slug driver because the URL is automatically generated based on the title and the user cannot customize it to something different. User profiles use a slug driver that automatically use their usernames as the URL (by default).
FoF Pages (just like Flarum Tags by the way) does not use a slug driver. Instead the slug can be manually picked by the admin when creating each page.
Supporting UTF-8 characters inside of the slug and final URL has challenges, but Flarum itself and I believe FoF Pages as well support it just fine. It's simply not used by default, because it can still sometimes cause problems with uncommon browsers or some proxies/webservers so it's up to the webmaster to decide if they want to use UTF-8 slugs in URLs or not.
The process of creating a basic "safe" ASCII string for use in the URL instead of UTF-8 is called transliteration. Flarum uses a very capable transliteration library when automatically generating discussion slugs. This transliteration library takes into account the forum language and has knowledge about many alphabets. It runs in PHP on the server side.
In FoF Pages, since the slug can be customized by the user anyway, a simple lightweight solution was used where a default slug is generated using a very simple javascript transliterator that basically just drops all non-ASCII characters. This is the same lightweight solution that Flarum uses to generate the default slug for tags since those can also easily be customized by the admin before saving.
I agree this lightweight solution basically only benefits latin alphabets and mostly just English, but it's really just meant as a starting point so the slug field doesn't end up empty.
So just write your title first, and then write your slug in the slug field exactly like you want it. FoF Pages will not change it back unless you edit the title again, in which case you can manually fix it again.
I hope this makes things clearer. I don't think you will have any issue after manually inserting your chosen slug.
If you receive an error message at any point, please share it with us.
