@dctopo: I am very happy to confirm that copying the key file content is indeed working here, too, I got my old keys imported! Thanks a lot for exploring that workaround!!
Some more information:
- It feels quite… well… random to me, that copying key file content instead of entire files makes a difference… But the DC devs might know why and maybe make that more transparent.
- I did not try the “minimize” gpg workaround. That wasn’t needed here probably because the keys were originally from DC itself.
- There is no way to install a fresh DC instance and select keys to be imported right away (besides starting from a previously created DC backup). So, I had to take care not to have DC continue with newly created keys while setting old keys up. Anyway, it seems that DC can handle multiply keys, though. See here.
- To make DC import old chats I moved the mail away and back to DeltaChat mail directory as mentioned already.
I am about to mark this thread kind of solved soon!