Under unix in general (linux, bsd and, I assume, OSX) you can change your system resolver as you please. DoH is supported by several implementations to a various degree already. You can switch right now, for everything running on your system if you wanted to!

But browsers nowdays basically live under the following assumptions:

- the users are dumb, and "we know what's best for you" (well, to be fair this has been a consistent trend for everything in the industry) - the OS cannot be trusted for anything, the baseline being the lowest common denominator of any old/broken version of android/osx/windows/linux they want to support - the users cannot change the system resolver even if they wanted to because the OS is locked down (android, ios, and windows with group policies)

I think all the above reasons are detrimental, but at the same time they're all sadly true. Because browsers essentially are now not far from operating systems, they abstract themselves above everything, including the resolver.

Is there some simple thing I can apt install on my Ubuntu system?

Since Mozilla makes a browser it was natural they'd try to solve it at the application level and not wait until M$ and other privacy loving OS vendors solve the problem.

> instead?

It probably should be, but the undertaking is massive (cross platform) and browsers want a quick turn around. A lot of people would think that VPNs solve such issues, but it just pushes the problem further up the network.

In my opinion Linux would be a good candidate for such an initial implementation - but you wouldn't pick DoH, you would likely offer DNSCrypt or DoT.