This seems a bit of an odd take. Matrix.org making their server freemium is up to them - charging some users to use the service (not the software) is a way of keeping the lights on. Better that than ads or selling user data. Lots of privacy focused orgs do the same - Proton, Tuta, Mailbox, Mullvad, IVPN. If people also have an issue with Element - don’t use Element, use one of the other apps.

If people are this upset, its not impossible (or even that hard) to migrate to a different server - or host your own.

The code on the card is covered so Amazon might know you use Mullvad but they have no way of knowing what your account is.

Mullvad know your acct but they have no way of knowing how it is you paid other than maybe it being a scratchcard which they don’t track anyway.