Opening fdroid.org creates a cert error - complains that cert is for f-droid.org, then if ignore this get a proxy error.
Tried bromite and fennec fdroid and loaded site without issue
I'm using official LineageOS with webview 75.0.3770.101
Updated by Soren Stoutner 6 months ago
This works fine for me (screenshot attached).
The most likely reason for the error you describe is that the internet connection you are using has a proxy filtering web access. The proxy is attempting to do an SSL Man-in-the-Middle attack. Privacy Browser is not impressed and produces an SSL error message. The web proxy is then not impressed at being caught and returns an HTML document with the proxy error text in your screenshot.
As such, I would recommend you try it on a different internet connection. Also, looking closely at the SSL error message will give you a lot of clues as to what is going on.