> I'd still be concerned about not being able to use the same key for proton mail and my desktop application
Would it be possible to use different subkeys for each (a good idea in any case, since it would allow revoking them separately in case one of them is leaked)? I don't recall whether the packet with the features and algorithms support information is attached to the key or to the subkey.
It's possible to do both, however, the crypto refresh recommends setting the preferences on the entire key, and anything else isn't widely supported, I believe. Theoretically, you could have two versions of the key with different preferences (and different subkeys), but at that point you're probably better off having two entirely separate keys.
Would it be possible to use different subkeys for each (a good idea in any case, since it would allow revoking them separately in case one of them is leaked)? I don't recall whether the packet with the features and algorithms support information is attached to the key or to the subkey.