Yeah .. I still think the original thought is probably roughly the right idea.
If there are no exposed options to work with then we are sorta outta luck in that direction.
Though I will mentioned that I have ungoogled-chromium here and the options listed above were derived and tested on that .. so I am fairly confident that its those 2 responsible for it there. I was able to temporarily block endeavouros.com using the hosts file.
( Also good kuz I keep that thing updated/filled with .. [ wc -l /etc/hosts ] .. almost 425K entries. 
)
We could work the other way around though .. by default cachy uses systemd-resolved resolver … you could try disabling or modifying that in the hopes that something works better.
See for example: