Guys, I took the time to test something
This is working in Joomla, but I am quite confident a similar solution can be found for WordPress as well
For Joomla, download the following extension
https://extensions.joomla.org/extension/n3t-multi-captcha/
That extension provides multiple captcha and other kind of protections. Among other things, it provides Honeypot protection, using https://www.projecthoneypot.org/
You will have to create an account on ProjectHoneypot website and generate your own API key here
https://www.projecthoneypot.org/httpbl_configure.php
After that, just select this plugin in AcyMailing Configuration, under the Security tab and you will have a HoneyPot protection in the AcyMailing Subscription Form