cpach

This is wrong in the modern sense of how the term is used. The vast, significant majority of rims sold and intended for use with tubeless tires rely on rim tape to form a seal with the spoke holes, which works fine, even at high road pressures (though it may take two laps of tape vs 1 for offroad pressures). What makes a rim designed for tubeless is the shape and tolerance of the bead shelf and the presence of a center channel for mounting. This is annoyingly somewhat inconsistently standardized--most everything on the MTB market works pretty well, on the road side things are pretty good these days but some combinations are really hard to fit, and some tires specify they must be mounted on hooked rims (some road tubeless rims are hookless), etc.