Browser: Make An Https Get Request To Api That Uses Self-signed Certificate. Programmatically Without Any Work On The User Side

I need to call an HTTPS REST API (Kubernetes) that uses self-signed certificates (almost all Kubernetes clusters are like that). I have the cluster's root CA certificate (and also

Solution 1:

How can I make this HTTPS GET request in browser and without user interaction (e.g. without asking the users to download and install the CA certificate)?

You can't do this with your setup. Browsers will only accept certificates issued by predefined trusted certificate issuers. If there would be a way to silently accept anything outside of this then stealth man in the middle attacks would be easy.

Therefore you have to options: make the user accept your certificate or get a certificate issued by a public CA. Given that such certificates can be free the latter option is likely the easier one.