This is only great open source alternative for HelpScout. Using this for events and collaboration between teams for small projects. Indeed its very good option compared to paid services if you want to keep an archive of your data forever and prevent data access by service provider.

If you need a help desk that you can self-host then FreeScout is one of the best you can use. It has almost all the features that you can expect from a Zendesk alternative. You just host it somewhere and then start using it. I really liked its interface and the features that it offers. The push notifications are nice and you can have unlimited mailboxes here and assign them to any user you want. So, if you are looking for a free Zendesk ot HelpScout alternative then you are at the right place.