There are many forums/discussion media out there that discuss crypto in general, but unfortunately the one that's currently synonymous with Bitcointalk is only Altcoinstalks.
If you are serious about discussing, you can go to several platforms such as subreddits that discuss crypto & Bitcoin SE (for technical Bitcoin-related things).
The forum era has died down the past decade or so, due to social media, Facebook groups etc. Till recently, I only knew Bitcointalk and it's currently the only forum I'm active in, I suspected that there might be others as well, but I never bothered, I wasn't interested in another one. From my perspective, there's no other place like Bitcointalk, I've also tried the other forum but couldn't stick to it.
A quick Google search would answer all OP's question, he'd find a few forums, either with cryptocurrency sections or solely for that purpose, but I highly doubt he'll find a better one, we're the most popular.