During our move from closed source to open source with the 3.0 version, we had to drop source code that is commercially walled in one way or another. We do have an open feature request for bessel functions https://github.com/arrayfire/arrayfire/issues/614
however we haven't had much progress on that front. Kindly follow the issue for any updates related to this feature. Hopefully, we will add them back soon.
Please upvote the feature on our github, the more upvotes we have, we will attempt to add the feature as soon as possible.
Thank you for your interest in ArrayFire.