@ryo This is definition of Free Software (What is Free Software? https://www.gnu.org/philosophy/free-sw.en.html).

There are 4 essential (0=run, 1=study, 2=redistribute, 3=modify).

This is definition of OSS (The Open Source Definition https://opensource.org/osd).

OSS has no 0=run freedom.

Free software is social movement for user free. OSS is software development method for performance/quality (by corporation).

I think FOSS is software license type (≒OSS). I think difference of FOSS and OSS term is not important. But difference of Free software and OSS is very important.

I think your request (privacy protection) exceeds over free software.

UNIX phylosophy is not related for free software (UNIX is not free).

systemd (GPL) and firefox (MPL) are free software license (https://www.gnu.org/licenses/license-list.en.html).

You can modify systemd/firefox by your self. You are not restricted by using systemd/firefox. And your free is protected.

If you want to priority privacy exceeding free software, you can select and modify existing free software.

I think your opinion (systemd/firefox is not free) is wrong. I am FSF associate member. So I cannot miss your wrong opinion.