Long story short:
We were forced to upgrade the kernel version for Raspberry PI, in order to support the latest model of Raspberry PI 4 v 1.5.
Unfortunately, for those newer kernels, there are no pre-built wi-fi drivers for dongles not already supported by PI. Those were built by a third-party which just stopped providing them.
We tried to support latest PI 1.5 by doing some tricks to retain wi-fi drivers, but it did not ultimately work.
So, we needed to make the choice: upgrade the kernel to support latest PI 4, or drop some wi-fi driver support. Considering that in the future we would have needed to upgrade the kernel anyway, we went for the first choice.
Of course, we could build and maintain those drivers ourselves, but it requires a substantial amount of work which we cannot handle at the moment, and we prefer to prepare a list of supported dongles that you can get if in need.