Have ad publishers pay users, instead of pay ad companies.

Instead of make an ad that already consumes the visitor's attention to also consume their cpu, and this to enrich the ad-tech company, consider making a website pay the visitor for having their attention consumed by the ad instead of pay the ad-tech company.

This would be open to abuse by visitors, where visitors reload a page over and over to get paid. To prevent this type of abuse, require visitors to submit money as collateral to the website. Users pay $x per month to be part of this "ad network". If users view and get paid for more pages than their submitted collateral, they keep the money the ad paid them but they don't get their collateral back. In a way this forces users to pick which pages to visit.

The likelihood that one of your visitors mine one bitcoin is extremely low nowadays. If you work in a pool that doesn’t consist of only your visitors and their limited resources, you will get close to nothing.

Just go burn a few old tires outside. The environmental impact might be similar and you will save time.

This was done using other coins (not bitcoin) that use cpu. People got creative used free websites that offered a preview of your site at different screen resolutions which would use the site's resources for the mining.

People still use it to mine while you are viewing a video. But browsers got around to blocking and labeling as this as malware.

For historical context 14 years ago it was an option: https://github.com/progranism/Bitcoin-JavaScript-Miner

Don't waste your time. You are better off trying to guess a bitcoin hash.

No. Bitcoin is mined with Asics (not even GPUs). Mining with CPU will bring roughly $0 per user and $0 per many thousands of users while burning the CPU/Battery/whatever of these users. Given that alts got destroyed as of late, this means mining as an ad alternative is as good as dead.

The really closest thing is something like stacker.news where users pay micro-dollars using lightening. There is also a podcast app. But from experience, these do not seem to scale very well.