Cloned their asl-dahdi out of tree driver and fixed up a bunch of things but it will won’t compile on any kernel later than 5.15. The project authors needs to fix it before you can even attempt to install asterisk. It won’t compile on the latest Raspberry Pi kernels either. Their last update for 1.x is 4 years ago in 2018 and their last update for 2.x is more than a year ago in 2021.
The entire project is not very actively maintained software wise. You really need to get them to fix both the kernel module and the userspace software. We cannot be engineering support for projects in the wild, especially when dealing with out-of-tree drivers. You can point them to this thread.