Some additional notes if anyone is curious:

I've also seen layout C on Role 4 Initiative dice (I fully recommend their sets with larger numbers and the 'arch d4's)

I know these are all the numerically balanced layouts because I ran an exhaustive computer search a few years ago. If your d20 doesn't match a layout above, it's not fully numerically balanced.

A die without this kind of layout isn't necessarily unfair! A perfectly formed d20 would be fair whichever faces the 1 to 20 numbers are on

And a key point I think is very important (and you're welcome to relay it to your DM if they get mad at you for dice that aren't numerically balanced or are even spindown/counter dice):

Dice don't usually need to be so fair! In most cases it is fine so long as they are fair *enough*.

Especially with RPGs, the point isn't perfectly balanced competition, the point is to have fun and come up with a good story. Almost any die is good for that!

@Sophie recently saw a clip about the usefulness of "emphasis dice" - you replace 18 and 19 with 20s, but also replace 2 and 3 with 1s. They were saying that more frequent critical successes and fails can be a fun way to add tension to extra impactful moments.

Unfortunately I only listen to TTRPG content and don't have a group (yet) so I'm curious what you think of that!