Sorry for the x-post, but did you try something like this?
Discussion
No, we did not. I didn't have the time to figure out FOSS software that would work between GrapheneOS and Ubuntu at the time. My point here isn't necessarily to solve this issue. There are of course many ways I could solve it for myself. But I don't have as many liberties while helping someone on a video call with their SS. The problem was that it wasn't possible to just sign a transaction in the moment and be done with it. It's a UX problem in my opinion.
Having a second option that doesn't require a camera would have moved us ahead right away instead of creating a roadblock to adoption. It's just a suggestion to add the ability to use an SD card. There could be other methods, that's just the only other method I'm familiar with from using other devices where I've had similar issues.