Pretix would be great. It's used by CCC, HCPP, Paralelní Polis.

Although for me it could be super simple. Actually I don't even need the sales system, only pre generated tokens and I can distribute the tickets myself. I organize very simple events. And I'd like to not even have email address or any other user info. So what nostr:nprofile1qqs9pk20ctv9srrg9vr354p03v0rrgsqkpggh2u45va77zz4mu5p6ccpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsz9thwden5te0dehhxarj9ehhsarj9ejx2a30qyg8wumn8ghj7mn0wd68ytnddakj7xph5zr created is even better than pretix, where there's a more complicated sales process with t-shirt sizes, email addresses, name tags. 

I just need "one entry, not used yet, valid".

Can't wait to try it out.