Access my IPv6 hassio from IPv4 addresses

Hey,

my ISP only provides an IPv6 address and I got SSL with the NGINX Proxy Manager running.

I had a few problems over the last months accessing my hassio, because the mobile carriers in other countries do not have IPv6 enabled, also in a lot of hotel/airport wifis there is only IPv4.

I tried now with an portmapper to access my hassio.
I do get an connection to the webinterface, but since its not a SSL connection, I’m not possible to login.

My current configuration looks like this:
own domainname “ha.domain.com” with an AAAA record to my hassio
NGINX Proxy Manager Host from “ha.domain.com” to local hassio IPv4 “192.168.178.2:8123” with an Let’s Encrypt Certificate.

Do you have any ideas how I could create an Let’s Encrypt Certificate, so I’m able to login?