I’m using NextDNS for DNS encryption and Avast Premium for antivirus. I noticed that my Mac was sending strange queries—about 4,000 per month—to mobile.de, a German auto dealer I haven’t visited before. I investigated and found that Avast was sending these queries. However, I thought my computer might be infected, so I formatted it. I took a backup, erased all data from the disk, and installed macOS from scratch. First, I installed NextDNS, then Avast, and the mobile.de queries started again. I completely uninstalled Avast, and the queries stopped.
Stay away from Avast. I don’t think they are private and secure.
P.S: I bought Kaspersky. I had to deactivate Avast’s proxy and filtering for NextDNS to work. With Kaspersky, I don’t need to do that. NextDNS and Kaspersky work together without any issues.