We’re aiming to release the next version in the next couple of weeks. If you want to test beat callbacks in version 2.00.13, you should be able to fix the compilation error by selecting Assets/Plugins/FMOD/src/Runtime/fmodplugins.cpp and enabling Switch in the inspector:
Thanks for your patience, and sorry to hear that this is still not working for you. Testing here indicates that timeline callbacks are working on Switch in the latest version of FMOD, so perhaps the problem lies elsewhere. Would you be able to send us your source code so we can try to reproduce the issue here?