I would personally not mount a tire without a tube on a rim that does not have a "H2" marking (
https://www.tyresizecalculator.com/w...wheel-markings).
I was taught at school that the bumps on each side of a "H2" marked rim is safety bumps that hold the tire beaded in case of a puncture.
I understand that a tube will not hold the tire in place if all air is lost suddenly, but I think that it will help if there is a small puncture, you notice the puncture, and can stop the vehicle before all air is lost.
Rune from Norway