Top Upstreams shows DNS-Server, thats not in Upstream DNS Configuration - how do I find out which client does that

[TerminatorX42]

Hi all, my three upstream DNS-Servers are

> # Cloudflare 1.1.1.1
> https://security.cloudflare-dns.com/dns-query
> # DNS-Forge
> quic://dnsforge.de:853
> # QUAD9 ungefiltert ohne ECS
> https://dns10.quad9.net/dns-query

Still, the overview shows:
Top Upstreams (last 7 days)
185.228.168.168:53 74.85484.41%

(Thats family-filter-dns.cleanbrowsing.org, but I am not knowingly using that anywhere?)

How can I find out what/who is behind that?

Thanks,
Paul