Though if a player were to ask to roll a d30 instead of a d20...I might allow it for a single roll provided they have a physical d30 on them. XD If only because that would be a very interesting dice to see.
I have one. I don't remember what it was for, but I used it back in the AD&D days.
Created an interactive character sheet for sidekicks on Google Sheets - automatic calculations, drop down menus for sidekick type, hopefully everything necessary to run a sidekick: https://tinyurl.com/y6rnyuyc