Wow, what an awesome dive into some of the technical aspects behind one of my favorite tools for using the web. And I do think of it that way these days, it's fairly stunning on some sites to switch off all the block and see how they become genuinely unbrowsable. I remember seeing Gorhill discuss a few times over the years some of the reqs for uBO during certain times (like why it could no longer work with Safari following changes Apple made a while back), but so cool to have it all collected in one place.
Having said that I've also been fairly stunned recently to see how much difference a simple DNS blacklist system can make too. Not because it's a big technical achievement but because it isn't and in principle seems relatively trivial to work around. But as I've been switching all my routing from UniFi to OPNsense, I've gone ahead and tried out Unbound's basic built-in blacklisting. While it's no uBO, it works on every single device and browser including in apps and it seems like it really shouldn't, that more parties would just be proxying ads through their own infra and DNS. Been kind of an interesting illustration of technical vs economic influences in an ecosystem. I can see how proxying would add complexity and cost to setup so it must just be that few enough people do it the ad industry can't be bothered.
But should that ever catch on (and it could, Raspberry Pi seems fairly well known) I expect uBO to be able to keep up with the cat-and-mouse long after DNS has been left behind. This piece helps underline how incredibly important maintaining a critical level of diversity in the browser ecosystem is. Just shortly ago there were a bunch of complaints again about Apple not allowing Chrome to be on iOS because it "holds back the web", but what "holding back the web" looks like is certainly a matter of perspective...