Fake Sign Ups - in need of some sort of captcha

[johnkenworthy]

Getting many fake sign ups on a regular basis. Recently about 100/day. These are possibly genuine emails - but not genuine sign ups (most are pornographic). They do "tick" GDPR consent, and no they do not double confirm.
I find out because the system send sme an email congratulating me on my growing list and I will soon need to upgrade my account for the new sign-ups.
Can we implement some form of Captcha, or honeypot that would reduce fake sign ups/bots from even submitting the form?