That is the distinction between Open Source and Free (as in Freedom) Software. I prefer the spanish/latin/french term Libre to refer to what you call “truly open source”.
Open source is indeed frequently used by big and smaller companies to do what I call OpenWashing. Yes the source code is available somewhere but the licence is so restrictive that it doesn’t respect my freedom and thus isn’t Libreware / Free Software.
Also copyleft for the win!









Maybe memoria but I don’t think it support e2ee. However it is a self-hosted solution which is more private than a unecrypted SaaS with tons of telemetry.