Some of these like detectprotal are for checking whether internet is working (IPv4 and IPv6), others are for loading remote data that is used to configure Firefox (services.mozilla.com). There might also be extensions that contact to specific websites like the ones that do not have Mozilla in their URL.

See:

• https://support.mozilla.org/en-US/kb/how-stop-firefox-making-automatic-connections

thanks, that at least brings some clarification.

however, that still does not solve the problem for the "non-mozilla" sites:

  firebaseinstallations.googleapis.com
  app.adjust.com
  o1069899.ingest.sentry.io

how can i disable these?

You can search the about:networking page for those websites and also do a Google search.

• https://www.google.com/search?sa=X&num=100&q="o1069899.ingest.sentry.io"

Could be about GCP (Google Cloud Platform):

• https://www.google.com/search?sa=X&num=100&q="firebaseinstallations.googleapis.com"

I noticed you filed a bug report:

• 1897900 - Analytics (Mozilla,Sentry.io/Adjust/Firebase) need a gdpr compatible Opt-In Banner

hi cor-el,

thanks for your post. however this does not answer my question:

how can i make sure, firefox does not make a connection to?

 firebaseinstallations.googleapis.com
 app.adjust.com
 o1069899.ingest.sentry.io

thanks

If those connections still happen in Troubleshoot Mode and in a new clean, unmodified, profile then those connections are likely used internally for storing data on cloud servers remotely and they are required to make Firefox work properly.