I wouldn’t actually selfhost email, it’s not particularly easy and there are many issues you will probably encounter. I recommend ProtonMail, it’s $3.50/month if you only need email and for $8/month you also get calendar, cloud storage, a password manager and a great VPN. Also, they are very focused on privacy and encryption and their apps are open source. Alternatively you can go with IVPN or Mullvad, both are great. Digitalocean has been fine in my experience, have you had any issues with it?

Something like StackOverflow/StackExchange would be nice. Would also like to see a federated platform for designers/artists (some Dribbble or Adobe Behance alternative).