@felmue There's no exact information on compatibility in your links.
I found problems, then contacted directly M5 and they explained that Core2 and GoPlus2 are not compatible in a direct message.
Hope this thread helps next people.
BTW, I bought a new Core Gray device (Core1, not Core 2) but still GoPlus2 is not recognized.
I'm starting to think I'll never make it work... :'(