I have not run TTRPGs at conventions but I have run card and board games. I like introducing new players to games I enjoy and I think I pretty good at explaining rules to new players. I've never felt comfortable running TTRPGs at tables people pay to play at and I never really like Adventurer's League. What I have done is posted for running one-shots at my LFGS to run games that I otherwise wouldn't have time to run as a campaign and which not all of my normal group are interested in. For example The Expanse. These have gone well, but it helps not to have the pressure of making the session worth taking up a slot of time in an event people paid for.