At least ss is an acceptable and widley understood replacement for ß.
My last name end on "ić" so every time, even on many EU shops and websites, I get to choose if I want to write my name wrong with "ic" and definitley get the package(cause the post understands) or write my name properly and get my package in 90% of cases.
Its just plain weird that a Spanish/French/UK online shop will support their weird characters but not full Unicode.