How to prevent DNS leaks with Firefox on Linux

[pipox9 0]

Interesting topic.
I would like to understand how I have to configure Firefox / AirVPN in order to avoid any leaks.
Either I misunderstood the following or I made some mistakes. When I connect to ipleak.net, I can clearly see that I am using a AirVPN server as IP address, but in the DNS Addresses area, I can find other countries in the server list (the actual country I am in + the States for Google servers). Should they not be only AirVPN DNS servers?
I am using Eddie 2.21.8 in a Linux system.

Thank you

[SurprisedItWorks 49]

Of course make sure "DNS over HTTPS" is off in Firefox settings.  Perhaps Mozilla is defaulting to ON and using Google DNS these days.