@chrisisgr8
Twitter: Mastodon (duh)
Reddit: Dunno just yet, but forums or maybe Lemmy
Discord: Any privacy-respecting IM (Signal for individual conversations or group convos with people you know IRL, something else for group convos with people you don't know IRL)
Youtube: creator-owned platforms (Nebula, Dropout, etc) or ones that compensate more fairly (e.g. Qobuz for music)
Search engine: DDG, but I know it's not perfect
Windows: GNU/Linux