>Yes, the typing of umlaut is a problem.
It is no problem at all if you know the trick. You can substitute the Umlaut by inserting an extra "e".
ö = oe
ä = ae
ü = ue
This is a perfectly correct and accepted alternative spelling which became popular in the times of the first typewriters which did not have keys for the Umlaute. (In fact, the roots are much deeper, the dots on the vowel derive from a little e that was written above the vowel in late medieval handwriting.)
Simply omitting the Umlaut as the English speaking world, including our dear TripAdvisor, prefers to do is not allowed and may lead to misunderstandings and detours. Münster and Munster, for example, are two completely different places, as are Rudesheim and Rüdesheim. Looking up train connections to "Fussen" also leads to confusion...