German Umlaute/Accents ö ä ü in URL-links?

Hi there,

if we use a German Focus Keyword like “Bäcker” (which means bakery) in English … how does the URL link has to be correctly? When we buy domains in German speaking countries we usually buy it with a slightly different spelling.

Example domains:
=> Name of client: BÄckerei MÜller
=> Domain we buy: http://www.bAEckerei-mUEller.at

Question concerning Focus Keyword URL:
=> Focus Keyword in RankMath should be: BAEckerei MÜller
=> URL of subpage is e.g. => http://www.xxxxxxxx.xx/bAEckerei-mUEller => RankMath doesn’t accept this new spelling and leaves red cross, though it would be correct for German speaking people.

How should we handle such Focus Keywords with ä ü ö in them? How would Google like this issue to be handled best?

Thanks in advance and best regards from Austria