From reading the overview of the MLxi, it appears to just be for when you have non-Phonak hearing aids, but want to use Phonak FM accessories. There might be more to it than that, though.
Some donation routes might desire that you believe the device is working. However, I suspect you can donate it to the Lions Club (tax deductible) which has been accepting hearing aid donations for decades. They will happily take broken aids, too, by the way. However, If you search the Internet for “donate hearing aids,” you’ll find that “everyone” wants your aids. Presumably, many of the organizations will also take an iCom for when they have compatible aids to give to someone.
You also might consider holding on to it for a few months before doing anything. A situation might arise that can be helped by the iCom. It’s value isn’t going to drop over the next few months. From what I’ve read, there are some things people do that can’t be done without the iCom.
Did you check its warranty? Even though your dispenser may not take it back, perhaps Phonak will.
Lastly, in lieu of finding a highly capable professional techie that can figure out if the iCom is working the way it is supposed to for you and talk to you about it, if you know a techie person (e.g., young relative), he or she might be willing to dig into this for you at your house with your aids, the iCom, your TV, and all the manuals.