I use tuta mail and tuta calendar for mail and calendar, Vivaldi as browser on laptop, and Firefox on android. Bitwarden as password manager and bitwarden auth as 2fa. Use obsidian for notes and appstore is aurora store and droidify, I use archlinux. And for "cloud" storage, actually a backup I use This USB drive not cloud Buf works for me. Still kinda dependent on proprietary messaging platforms, but I have 1 friend on signal. Also I am trying to replace YouTube with fmhy.net not exactly YouTube alternative, but has so many resources for free to study, educate myself, or just watch something out of amusement.
Matrix is good for those situations, there are bridges to pretty much everything these days.