I use Gentoo GNU/Linux. Avoid Windows and macOS, instead use any GNU/Linux distribution or *BSD variant. If you want a 100% free system check out the FSF endorsed distributions
Don't use one, instead use Tor or I2P, if thats not an option; IVPN, OVPN or Mullvad VPN preferably via Monero or cash
If you like Firefox switch to LibreWolf or use a custom user.js, if you like Chrome switch to Ungoogled Chromium, if you want something minimal with Vim keybinds use qutebrowser. I've used all three, and can't recommend one specifically.
If you want something modern with multimedia, screenshare VC and encryption use Matrix with the Element client, if you don't like electron use nheko. You could also use irc/xmpp.
I personally use LibreX (instance). Wiby is also very cool.
If you want to self host use cgit. Otherwise everything isn't great, Disroot looks promising.
I personally use Neovim. If you need a GUI, I'd recommend VS Codium (libre VSCode).