Depois de executar minhas anotações quando criei originalmente a chave PGP há alguns anos, encontrei esta resposta em Ask Ubuntu:
$ gpg --keyserver keyserver.ubuntu.com --recv-keys 245FD525
gpg: requesting key 245FD525 from hkp server keyserver.ubuntu.com
gpg: key 245FD525: public key "my_name <my_e-mail>" imported
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0 valid: 1 signed: 0 trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
$ gpg --no-default-keyring -a --export 245FD525 | gpg --no-default-keyring --keyring ~/.gnupg/trustedkeys.gpg --import -
gpg: keyring '/home/ubuntu-xenial/[user]/.gnupg/trustedkeys.gpg' created
gpg: key 245FD525: public key "my_name <my_e-mail>" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
$ gpg --list-keys [user]
pub 2048R/245FD525 2016-12-16
uid my_name <my_e-mail>
sub 2048R/4D0AABD3 2016-12-16
$
Agora, posso usar minha chave PGP do Launchpad no outro computador.