Hardened NextCloud Deployment [Possible with my Scenario?]

I’m trying to figure out if I can accomplish a hardened Nextcloud deployment using VPN to circumnavigate ISP’s CGN and a lack of a private IP. I’ve spent hours researching and haven’t gotten anywhere.

Objective
â—Ź Deploy Nextcloud 13, hardened, and accessible at domain: DOMAIN.com
● I don’t care how I get there (likely Ubuntu VM), but of course pf is heavily involved.
● I have two issues: (a) I can’t connect the internal Nextcloud IP to DOMAIN.com and (b) I can’t use certbot to obtain SSL
Scenario / Constraints
â—Ź ISP
â—‹ Single provider available to all units in condo building, cost = HOA dues pass through
○ Static IPs offered @ $20/month (which I can’t bring myself to do for a number of reasons)
â—‹ Ethernet to structured media enclosure, no modem to place in bridge mode, etc
â—‹ CGN being used
â—Ź VPN
â—‹ Provider = TorGuard / Port Forwards offered if port > 2048
â—‹ OVPN Client #1 = TG_Static = Shared Public IP w/ port forward
â—‹ OVPN Client #2 = TG_Dynamic = All other traffic
â—‹ Why?
â–  TG_Static was set up as a test case / future use to facilitate the objective
â–  Port 32400 Forwarded via Torguard / pfSense Port Forward created / Test Case = Pass

Is what I’m trying to accomplish achievable? Items I’ve looked into, but haven’t been able to piece everything together.

â—Ź Use VPN to bypass CGN (similar to Plex test case).
● VPN “443” Port Share (requires option added to VPN client and allows web server traffic to flow through to localhost:443. Haven’t been able to get this to work yet.
● I know Apache can be set to “listen” on a port other than 443. But I don’t think this allows the certbot script to succeed.
â—Ź ACME package. I have successfully edited DNS text record to achieve validation.
â—Ź Reverse proxy / HAproxy pf package. Unfamiliar.

As you already want/need to use an external service to get to your Nextcloud installation you might be interested in Beame-insta-ssl which is also available as a Nextcloud app:

https://apps.nextcloud.com/apps/beame_insta_ssl

In the range 20$ you can already get the first dedicated servers and surely virtual servers in a data center with a decent connection. VPN can be a solution if you want to run it at your place, but with a decent speed you probably have to spend a few dollars per month so you could use a vserver as well. If your provider gives you ipv6, you could still use storage at home via external storage.

If it is just for the certificate, I think you can go through a DNS entry to verify that you are the owner.

Ports: If you want to use Nextcloud on your mobile and other clients from different locations, I would only use the default SSL ports because in many free Wifi connections (perhaps some mobile providers as well) do not allow connections other than standard http(s) ports.