Sell a service rather than sell your users and suddenly the bots are far less of a problem. In essence make users pay, bots will become shy

Captcha's, rate limiting, slight changes to the way you interact such as changing words, changing positions, etc.

This is a solved problem, but these things create friction for the user. And friction is the opposite of what modern tech says you want to provide to your user.

Get them to endlessly scroll, comment thoughtlessly.

Allow bots but also give users the tools to filter out bots that Twitter keeps to itself.

You send out a mass DM asking if this account is not a bot to not respond.

Just kidding but this happened to me when I used IRC back in around 1993-1994. For some reason I would respond anyway and would get banned for a time.

there isn't one. but that's irrelevant because the services that require your phone number don't do it for the sake of security or to combat bots, they do it to gather data. when you give a megacorp your phone number, they get your real name, your relationships, and a myriad data points to sell.

this is the reason why all megacorp mobile apps and every other free flashlight/calculator/alarm app require access to your contact list.