PSA : The first Palico/Prowler level cap break is the HR4 Palico Quest "The Grandmeowster's Trials".

Title. It's nothing hard too. Killing 15 Konchus.

It raises the max level to 35. I don't know if there's another. Next cap breaks with the HR7 urgent, to 50 apparently. (Thanks u/Laxaria)

I couldn't find the info, either on the sub or on Discord or goddamn anywhere that wasn't all about moonrunes, so I felt like a PSA was needed. Hope it helps my fellow Prowler mains stuck at 20.