This is a good comment. There are I believe a couple more cases where HTTPS is difficult: - You use a dynamic subsubdomain scheme. E.g. abc.xyz.example.org. A wildcard certificate for *.example.org only covers xyz.example.org, not abc.xyz.example.org. Requesting a certificate as the page is requested is possible, but will cause a lot of latency, and you will probably hit the Let's Encrypt rate limit; - You embed resources that are only available over HTTP and cannot be proxied, either for technical or legal reasons; - You request resources from a local IP address, e.g. a website hosted on GitLab Pages that shows you the data from your own DIY weather station which runs in your local network.

These cases are not that common, but that does not make them nonexistent. 99% of websites don't fall under one of these cases (there are probably some others I have not even considered), and should probably support HTTPS.