Are the farting and burping normal?

In USA, not a minor and no financial constraints or issues with vet access. My cat (9, male, neutered, indoor only) has been having ongoing allergy issues and recently switched to Rx hydrolyzed protein food. We tried Hills first, but he stopped eating completely after a couple weeks, so we switched to the Royal Canin version. He loves it, but after a few days eating the new food, he is farting constantly. It smells horrible. At first I thought he had poop stuck in his fur or something but he is totally clean. Pretty sure he's quietly burping as well based on the smells coming from his mouth. He is eating and using the litter box (bowel movements seem normal, if a bit larger than usual) and doesn't seem bothered at all. I've had gassy cats before, but this one never has been.

Is this normal or cause for concern? And if it's normal, could this be a temporary thing while his body adjusts to the new diet, or is this my life now? 🤢