I'll try it. I had tried it years ago and it was too complicated for my clients (lawyers, accountants, real estate agents etc.) so went with something simpler. It is simpler if I use what they use. But, I'll try it again.
Added Nov 5 2021: Well, I'll be darned. With Ublock Origin, even in normal easy mode my clients could handle, NO ADS! Not even in search results. Thank You. Now I've got DDG search and no ads.
@legobuilder26 Indeed. To elaborate a bit more (with my limited understanding), web applications are already able to detect if their tab currently has focus. Detecting this does not require the idle API.
The idle API goes further, allowing the web application to know that you have not been interacting with your computer at all recently, or that you have locked the screen.
Just another article on this uneven battle.
Special browsers like Tor guarantee anonymity and the exact same fingerprint across all users; for those that take privacy to the extremes, this may be the only option.