There is an awful UI problem on iOS and Android with type=number: they both allow invalid values to be entered, but the value given is just "" blank.

The user thinks they have typed in something valid, but JavaScript (or value from form submit) only gets to see "". E.g. use a thousands separator or paste in a trailing space and you will get an error "input must not be left blank".

There are worse issues with the less common input types.