I’d agree with this, you don’t necessarily even need to ask to join the conversation though they wouldn’t appreciate you taking it over. adding to what they are saying and join the conversation the same way you merge lanes in a car. match speed / context, and give them plenty of space to keep going as they were. watch for signs they don’t appreciate the interruption though, shared looks between them, annoyed expression, short answers, turning away from you etc. if they’re annoyed, no big deal, bow out of the conversation as gracefully as you can, apologise if they actually say the interuprion is unwanted or anything
good work picking up that it may have been an opportunity to meet people, now you’ll have an idea what to be aware of next time. try not to.overthink it.