It is much easier with dice, you can roll a D20 then take the remainder dividing by Dn (plus one). But you must avoid modulo bias (https://stackoverflow.com/questions/10984974) and re-roll for high rolls, which may be dissatisfying to players who roll a natural 20 on their D6 throw and need to roll again.
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This reminds me of one of those dice I saw that can roll anything from a D4 through a D20, if not more. Technically usable, but ... complicated.
a lot of fun dice here https://www.mathartfun.com/dSpecial.html
I like the "go first" dice
It is much easier with dice, you can roll a D20 then take the remainder dividing by Dn (plus one). But you must avoid modulo bias (https://stackoverflow.com/questions/10984974) and re-roll for high rolls, which may be dissatisfying to players who roll a natural 20 on their D6 throw and need to roll again.