The point is that there are plenty of captcha services and self hosted captcha software libraries that don't leak information to Google.

Are they still the 'squiggly letters' solution or have done something better?

"Squiggly letters" are still fine. There's a lot of FUD around AI & ML breaking them but I have yet to find an off-the-shelf tool that can break them; and so do the spammers.

Sure, you might break them if you pay a team of computer vision scientists for a few months but that isn't profitable for spammers, so even though they are technically breakable, in practice they're still good enough to thwart spam & bruteforce.