I’m trying to use the old Yamaha SYXG50 software.
Has anyone done this or know of a way to do this ?

If its in vst format, you could try jbridge? All my 32bit vsts work with jbridge

I’ve tried with Jbridge to no avail
It works using a vst midi driver in Cubase 5 (32 bit) fine but not Cubase10.5