Let me tell you about the foss-north 2020 community day. It has been an idea for many years, but it all started last year. The idea is that we welcome open source projects to a day of hacking, workshoping, teaching and fun the day before the conference.
The community day is free of charge. It works thanks to the volunteers from the projects, and all the companies helping us with venues.
You are of course very welcome to join the conference days too. For them you will need a ticket. You can learn more here: https://foss-north.se/2020.