What I use to force the old keyring format is to export a public key to a file and rename that to pubring.gpg. And of course delete the pubring.kbx.

Hi gniibe

Thanks, gniibe, for the quick reply.

Thank you for reporting. Sorry, I couldn't understand some part of your report. Perhaps, due to some terminology.

There are four things: primary key public, subkey public, primary key private, and subkey private.