This was discussed numerous times elsewhere in the forum. It seems there is no single good solution - every solution proposed requires manual changes to the configuration and none is integrated correctly right now. The solutions range from using pi-hole to manual configurations. The tutorial linked here seems to be the most complete instructions for pi-hole:
There is also this older overlapping discussion:
The pi-hole-based solutions require delegating your DNS to the pi-hole proxy, something I would prefer to avoid myself, as I have other delegations that may conflict with that.
There are tutorials on how to setup adblock instead:
Adblock seems to be simpler than pi-hole, there is a “RPZ” file that can be plugged directly in the Knot resolver which means minimal configuration:
Then there is this tutorial on how to manually build a blocklist for the Knot resolver, without the adblock package:
In the following survey, Pi-hole arrived slightly ahead (+10%) of Adblock as an ad-blocking solution for Turris software:
I myself am not sure which solution I will deploy. I am tempted to agree with some of the voters in that poll saying that we should choose the simplicity of adblock, but i’ll see how well it actually works in practice.