This is a FOSS alternative that looks decent for public events https://www.attendize.com/ but I feel like anything focused around "ticketing" will feel odd for small events. "Did you get a ticket for my birthday party next week?"

I would feel weird getting a ticket for my friend's birthday party or backyward BBQ, but this does seem to be a decent suggestion for more public events. This looks like a decent FOSS alternative, though I haven't tried it https://www.attendize.com/

Very cool, doing something like this has been on my list of Arduino projects for a long time.