I'm trying to install WordPress with CF's Flexible SSL option, and it worked out! The website loaded just fine with SSL. However, I couldn't login to the admin page. When inputting details, all the page did was refresh and cleared the input. No errors on the page or in the PHP errors log.
So I researched how to and I've found the best way to fix this was to install a CloudFlare SSL plugin on WordPress.
However, I can't install without adding logging to Admin so I went ahead and changed Site URLs, other URLs to the http version of the site's URL as well as disable SSL on CF's side.
This produced a broken website and errors in console:
Mixed Content: The page at 'https://example.com/' was loaded over HTTPS, but requested an insecure script 'http://example.com/wp-content/themes/twentyseventeen/assets/js/skip-link-focus-fix.js?ver=1.0'. This request has been blocked; the content must be served over HTTPS. I tried to fix this by purging cache but that didn't do anything.
And I still can't login to admin.
What can I do to fix this?