TLDR:

• Update: the server software has a bug about generating+saving certificates. Bug has been reported; as a workaround I added the local IP to my local 'hosts' file so I can continue (but that does not solve it of course).
• I suspect there's a problem with running two servers off the same IP address, each with their own DNS name?

Problem:

• When I enter https://my.domain.abc into Firefox, I get an error ERR_SSL_UNRECOGNIZED_NAME_ALERT instead of seeing the site.

Context:

• I have a static public IP address, and a Unifi gateway that directs the ports 80,443 to my server at 192.168.1.10 where Nginx Proxy Manager is running as a Docker container. This also gives me a _Let's Encrypt certificate.
• I use Cloudflare and have a domain foo.abc pointed to my static public IP address. This domain works, and also a number of subdomains with various Docker services.
• I have now set up a second server running yunohost. I can access this on my local LAN at https://192.168.1.14.
• This yunohost is set up with a DynDNS xyz.nohost.me. The current certificate is self-signed.
• Certain other ports that yunohost wants (22,25,587,993,5222,5269) are also routed directly to 192.168.1.14 by the gateway mentioned above.
• All of the above context is OK. Yunohost diagnostics says that DNS records are correctly configured for this domain. Everything is great (except reverse DNS lookup which is only relevant for outgoing email).

Before getting a proper certificate for the yunohost server and its domain, I need to make the yunohost reachable at all, and I don't see what I am missing.

What am I missing?