Is reCAPTCHA v3 the one that has the chance of forcing you to use a Google or Apple phone to scan a QR code even if opening it on a PC?

Workers are great for this sort of thing and these days with Turnstile and Email Sending beta[1] you can have Cloudflare handle it all

1 - https://developers.cloudflare.com/email-service/

Google has reduced the free tier limit for reCAPTCHA v3 from 1 million down to 10,000 assessments per month as part of its mandatory migration to Google Cloud. [1] So basically it's NOT a viable anti-spam mechanism for many use cases any more because that 10k asessment is easily breached. Let alone the fact that you can't use recaptcha v3 unless you signs up for Google Cloud as well.

Cloudflare Turnstile is a valid alternative though. [2]

[1] https://docs.cloud.google.com/recaptcha/docs/migration-overv...

[2] https://www.cloudflare.com/products/turnstile/