App "Gpg Mailer" cannot be installed because the following dependencies are not fulfilled

[serversghost]

Hi, can you please tell me which libraries I am missing, or that are required to install Gpg Mailer.
I get the following error when I try to download & enable Gpg Mailer from the Nextcloud app page:

App "Gpg Mailer" cannot be installed because the following dependencies are not fulfilled: The library gnupg is not available.

My server is running:

gpg (GnuPG) 2.2.19
libgcrypt 1.8.5

I've had a look around gnupg.org but I am unsure which specific library I require.
Any help would be great, thank you.

[tacruc]

I think php-gnupg so the php wrapper lib for php.