Is the 58mm size for the thermal printer just a straight up lie? Even 57mm paper doesn’t fit.
It’s not a lie.
I use 2-1/4" (57 mm) thermal paper in my DevTerm’s printer. I grabbed whatever weird brand Amazon offered me first when I searched for it.
That said, the novelty of having a receipt printer wore out pretty quickly for me. I ended up buying a bigger thermal printer (USB/BT) that can make labels too.
I bought a case of 2-1/4" paper rolls, billed as 58mm. They fit fine. Are you sure there isn’t some kind of obstruction?
NOTE: I just measured my paper and it is exactly 57mm. I doubt 1 more mm would make any difference.