Serial numbers for warranty claims, though commonly look alike characters aren't in the allowed character set... But if slashed zeroes where used, it'd add another character to the character set.
Last night my wife was trying to enter a Tesco (supermarket) voucher code in a website and got 0 and O wrong. The code she was emailed did not use a dotted 0. She was reading the code on her phone and entering it into a web page.
Daily, serial numbers for regulated cannabis lots have IL10O - humans reference them hundreds of times a day
Passports. German passport has alphanumeric number but no O to avoid 0/O ambiguity.
Yes. Is that only an issue in German passports or generally applies to all passports?
It is a rule for German passports. US passports don't have characters. AFAIK there is no general rule for passports.
Also, some passport numbers stay with you for life (China), other change with every passport.