A portable keyboard will work over either Bluetooth or plugging it in. I too seriously doubt you’ll find a custom fit keyboard case unless you make it yourself.

Unfortunately I’m beginning to feel that their business model and ability to support the device is compromised by the “value stacking” of trying to create an ethical phone that’s also repairable. It’s expensive (because of the ethics) so we have high expectations, those expectations are compromised by features inherent in the repairability, and they’re not able to devote the staff necessary to support the device. A focus just on repairability with off-the-shelf components would have resulted in a more reliable product that can be supported better, better parts availability, a cheaper device, and a fair part of the positive impact.

Not aware of anything like that no. I’m sure as you know, it’s fairly rare even for popular phones. You could try 3D printing sites where someone may have designed something and you might be able to get them to print you a copy.

Could it be that it’s switching between wifi calling and the wifi connection is dropping out, disconnecting the call?