Not the answer you're looking for, but reCaptcha is probably your best option. I attempted half a dozen mitigation strategies to prevent spam on one forum I ra

Not the answer you're looking for, but reCaptcha is probably your best option. I attempted half a dozen mitigation strategies to prevent spam on one forum I ran. I tried honeypots, questionnaires, other captchas, and proxying services to block bots. They slowed the bots at best, but when there's a torrent of bad actors it really doesn't matter if you slow them down 50%. I finally installed reCaptcha and it solved the problem instantly. Not a single bot has signed up in 6 months. I started getting suspicious that signups were just broken, but I tested it and it was fine. After that experience, I'm very much on team reCaptcha. I tried hCaptcha as well (on a different project), but found it was much harder to solve.