I honestly think it’s doable, i’m no expert and “just” follow the very good guides and tutorials here and there, I had little to no problem setting up discourse behind nginx, so I’m probably a bit lucky but I think it’s far from impossible 
I like these :
https://linuxize.com/post/how-to-install-nginx-on-ubuntu-18-04/
https://linuxize.com/post/secure-nginx-with-let-s-encrypt-on-ubuntu-18-04/
Thought it might not be an easy road to add to the mix multisite/multicontainer and s3 clone 
and for the combo postfix/dovecot
https://linuxize.com/post/install-and-configure-postfix-and-dovecot/