Porkbun is very good domain registrar. We can download free SSL from porkbun dashboard. All we need is to upload it into our VPS server and need to add the path of the certificates into virtual host file.
SSL
Host Multiple Sites with SSL in Ubuntu 18.04
In this tutorial we shall share all the commands necessary to host multiple websites in a VPS server. We used VPS servers from Linode and Digital Ocean. Both are excellent and best value for money.
Host Multiple Sites with SSL in LAMP
How to host multiple websites in a single VPS in LAMP environment. All sites will use SSL certificates (https). All commands are for shown considering Ubuntu linux.
Multiple WordPress with SSL in Ubuntu 16.04
Complete guide to host multiple WordPress sites in a LEMP stack in a Ubuntu 16.04 LTS. Installation of SSL by Let’s Encrypt has been illustrated also.
How to Add SSL to existing WordPress site in Nginx
This guideline is to Install single domain SSL (Secure Socket Layer) certificate in a Wordpress site running in a Nginx web server. No plugins are used. We bought SSL from namecheap.com.