I have played with a similar idea when I tried out AdGuard_MV3. Your idea worked reasonable well because I used AG_MV3 only for cosmetic filtering on websites I visit a lot. The bulk of the blocking is done in my browser (Edge blocking advertising and tracking networks) and my DNS (NextDNS privacy filters allowing affiliate ad and tracking networks but blocking many website specific stuff using NextDNS, AdGuardDNS and OISD filters).
I used the exact same rules (from NL also), but i made the allow exceptions for all websites which I had bookmarked or for which I had created cosmetic rules with AdGuard_MV3 red crosshair feature (which helps to create cosmetic rules in the user rules section of AG_MV3). Your rules would look like:
! your generic block rule
! TLD allow exceptions excluding my bookmarked domains
This has the advantage that I did reduce the third-party medium mode attack surface reduction for websites I normally don't visit, but keep the benefit of AG's blocklist for the websites I visit a lot (e.g. news websites and websites with IT-news). Using this in combination with DNS-level and browser build-in blocking it was a reasonable replacement for uBo's smart-medium mode (the thread of Windows_Security which is a sticky in this forum
). I say reasonable, because every time I added an exception, I had to add this domain to all eight TLD allow rules.
I guess we just have to wait and see how AG_MV3 and uBO-lite pan out. AG_MV3 is much more mature functionality wise than uBO-lite. It is also funny to see the different development principles of those two great extensions (AG-team focusses of functionality first and optimize afterwards, Gorhill focusses on optimization forst and offer functionality afterwards). When I had to choose right now I would opt for AG_MV3.