I am unable to import a key that contains only subkeys.

1

I am unable to import a key that contains only subkeys.
Not support only import subkeys？

2

OpenPGP transferable secret keys have to include primary key. How did you create a key without primary key?

3

I use GnuPG and when exporting keys, I use --export-secret-subkeys and “!” to specify subkeys.

4

There is a related issue on GitHub:

I closed it as not planned, Delta Chat does not support importing a subkey without primary key.