Self signed certificate to https connection

What are you trying to do? I do Not Unterstand why you would need ssl certificates on the watch?

Yeah...WAY too little context here.  "The Garmin" is a company.  Companies don't do connections.  Which thing made by "The Garmin" did you intend, and why are you asking that on this watch forum?  :-/

I think this is fenix 7 forum. But you're right, I really didn't write it specifically into the question.

Ah, starting to see.  It seems like you want to use a ConnectIQ widget for custom outbound https.  That is, I think you want to use something like https://apps.garmin.com/de-DE/apps/47f64742-cf59-4d54-b368-841a347f7c6d#0 (https://github.com/hasscontrol/hasscontrol#hasscontrol) maybe along with something like https://github.com/cyberjunky/home-assistant-garmin_connect to talk to Home Assistant.  So yeah, as @J said, the developer area is a much better place for this question.

I haven't looked at ConnectIQ much yet, but the watch widget github readme above clearly states that it goes through the mobile device, so the self-signed question may actually be a phone question rather than a watch question...again, I'm not sure yet.  See you over at ConnectIQ ;-)  But self-signed certs are easy to produce though, why don't you just try it?

(Edit) It looks like you're out of luck...again, this is a developer question, not a watch question.  But for example see this: https://forums.garmin.com/developer/connect-iq/f/discussion/4775/comm-makewebrequest-problem-with-https from over 5 years ago...note that non-self-signed certs are easy enough to come by nowadays.  Anyway, there is a lot of info about all this in the developer forum area.

Thx. But this is not good. The LetsEncrypt need port open and forward your firewall/router. Funny. Data transfer security with https but generate security hole with open port.

LE can be done over tcp/80 outbound. No security hole. Read through the configs, it's all there.