Chilkat recently added support for the cryptoCertum 3.5 smartcard (and also for cryptoCertum3, and cryptoCertum3.2).
At the time of this writing (13-July-2022), the support is available in a pre-release of the next version of Chilkat (v9.5.0.92)
We have it working on Windows, but should also be able to get it working on Linux and MacOS.