Thanks a lot to everyone! For now I have installed Discourse on domain omaggieconcorsi.online, I’m trying it a bit to see if it’s ok for my project.
I’m using this:
First impressions: it’s really powerful! even notifications via browser when a user creates a post :o
Then Onebox, very useful for me because I report promotions from other sites, so I just need to put a link and automatically show a preview image of the site and the link, fabulous.
Same thing for bookmarks (keep track of expiring contests, daily, monthly) and all settings on event dates.
I also glimpsed the possibility of uploading various images to external services (I also believe imgur) so as to save a lot of space on the disk (I have users who post photos of gifts received at maximum resolution, obviously not compressed or even resized).
The only things that block me a bit from using it: importing likes from mybb will be very hard (I’m still trying to import at least users and messages from mybb, but this in another thread); if something does not work with the server or I have to reinstall everything will be a mess (with a normal forum just save the files from ftp and the database and reinstall as it was before, but here I have practically nothing, everything is installed by DigitalOcean, I used their marketplace).
I don’t know 
Discouse really has many useful features that on other forums there aren’t, but on the other side I think it is dedicated to those who are experts in servers, Ruby etc. and who wants to keep up with the various problems. Only PHP and Mysql is simpler.