C0recollector, I would say this is the key:
“I called Chamberlain and the gal said it wouldn’t work with Ryobi.”
Why not? What is it about that Ryobi GD200 opener that makes it incompatible?
I did a quick Google search and found a few comments from people who confirm what you say, namely, that the Klik3u remote will not work with the GD200. But I am puzzled by why it won’t work. As you point out, the Klik3u remote uses one of the frequencies that the GD200 uses. So it SHOULD work.
The only thing I can think of is that all these companies - Liftmaster, Ryobi, Linear, etc. - don’t seem to want to play nice with one another, since they seem to be in a dog-eat-dog environment that is competing for garage door customers. So it may well be that Ryobi has slipped something into their garage door remote technology that makes it so you must use only their products. I don’t see any universal remotes that work with that GD200, but I could have overlooked something obscure.
I wish I had better ideas for you, but if the Ryobi GD200 has been designed to be as difficult as it seems to be with universal remotes, you may be out of luck. I am very curious what Ryobi has done to their remote that makes it so uniquely resistant to the normal solutions to this problem.