Why#
Danger
Without security, no privacy.
It is simple. Keep it simple. Mitigating digital security risks is not simple. So use GOOD the Open Security Architecture to find simple solutions for complex challenges.
Technology alone will never solve a single problem, but bad technical solutions do make it very hard.
Despite the privacy procedures, handbooks and process audits: Bad solutions make good procedures worthless.
The reasons to only accept FOSS technical solutions for protecting privacy related data are simple:
Open source(FOSS) is the antidote to surveillance capitalism.
FOSS software solutions are open and transparent.
FOSS solutions are easier to verify to see if it does what the creators say that it does.
Tip
For FOSS privacy solutions the used FOSS license matters.