I just noticed that the home assistant addon has been deprecated: https://github.com/hassio-addons/addon-pi-hole. I hope that it comes back eventually.
I also don't like it as AdGuard is a commercial company, and I have zero need for the added features like parental control.
But I don't really care, I run all the dockers that have nothing to do with home assistant outside of hassio anyway.
For me that means Firefox, uBlock Origin and pihole (though I ran dnsmasq myself for a while, I like what they've made of pihole now, it's come a long way!)