> but the one that bypasses the OS was forced by adtech monopolist in charge.
Assuming by “adtech monopolist in charge” you mean Google, I don't think taking control from OS would benefit them given they effectively have control of more than two thirds of the mobile market share globally¹ so they are shooting themselves in the foot as much as anyone else – so I assume there are practical reasons², or purely technical ones, for DoH being their preferred choice (assuming that are pushing a preference).
And anyway, there is nothing that says applications have to implement DoH instead of letting the OS do that, Chrom{e|ium} and FF have gone that way in part because base OS support wasn't (isn't?) commonly available/enabled.
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[1] A less than two thirds if you only count the US, as some published figures do, because Apple does rather better there compared to global averages.
[2] isn't dnscrypt's standard still officially a work-in-progress?
