There are also crib rail covers. They’re cloth and just tie over the rail so if they do chew, they don’t damage the crib
Saw this pop up in my feed and wanted to comment! I’ve heard good things about chewy things from ARK for kids who are sensory seekers. https://www.arktherapeutic.com/oral-motor-chewing-tools/
There are also plastic rail guards. More sanitary are you can take out and wash quickly.