Install OpenVPN Access Server on Debian

1. Log into the Debian device
2. Run the following commands in a terminal:
   sudo apt update
   sudo apt install ca-certificates wget net-tools gnupg
   sudo wget -qO - https://as-repository.openvpn.net/as-repo-public.gpg | sudo apt-key add -
   sudo apt-add-repository 'deb http://as-repository.openvpn.net/as/debian buster main'
   sudo apt update
   sudo apt install openvpn-as
   sudo passwd openvpn
3. Set a new password for the openvpn user
4. Open a web browser and navigate to https://DNSorIP:943/admin
5. Login with username openvpn and the password set earlier
6. Click the Agree button to accept the EULA
7. Click User Management > User Permissions in the left navigation
8. Create a new username and click the Admin checkbox
9. Click the Save Settings button
10. Click the More settings button on the row of the newly created user
11. Set a local password, scroll down and click the Save Settings button
12. Click the Update Running Server button
13. Click Logout at the bottom of the left navigation
14. Log back in with the newly created user
15. Click User Management > User Permissions in the left navigation
16. Check the delete box on the row of the openvpn user
17. Click the Save Settings button
18. Click the Update Running Server button

Source: https://openvpn.net/vpn-server-resources/installing-openvpn-access-server-on-a-linux-system/#Install_repository_then_upgrade