Style / Language / German says:
"As noted in the Wikipedia article on Eszett, ß is the only European letter that does not have a corresponding capital letter (not yet, that is). Since it never appears at the beginning of a word, there is no need to convert ß to SS (or SZ) for capitalization. However, when correcting the capitalization of a title that is in all uppercase, it may be necessary to convert SS to ß (e.g. Rammstein's "WEISSES FLEISCH" should be capitalized as "Weißes Fleisch"). Please note that the use of ß has changed after the 1996 spelling reform (most important: new spelling dass and muss instead of daß and muß, but still ß after long vowels, e.g. groß, and after diphthongs, e.g. weiß)."

This is pretty outdated, there has been a majuscule form of ß (namely ẞ) at least since it was introduced ~2007 or so in Unicode 5, IIRC.
Since 2010, it's use (over SS) is use is IIRC even mandatory in some areas (official documents of at least some governmental agencies).

So that section should perhaps be updated.