I am in search of a better web clipper myself as I have not found the perfect solution. I am not sure about password protected sites.
Most recently I have been depending on the browser plugin single file, which is often overkill as it saves entire pages. At one point I used a plugin called "scrapbook" which I recently found out has been resurrected by a developer as "scrapyard" I have not looked deeply into it. It seems to be well thought out and provide some interesting workflows to save bookmarks and webpages locally. It also has a android application. I believe the developer uses orgmode as their personal knowledge manager and scrapyyard ties into that. It is open source.
https://addons.mozilla.org/en-US/firefox/addon/scrapyard/I have also used zotero which did a great job capturing entire pages. It seems it might be a possibility because many academic works that someone might want to collect content from are behind gateways requiring passwords.
There was a period that I was using tagspace's web clipper. It allowed me to be more selective about what I was selecting from a page, and it saved the clipping locally as a html file which I could link to locally if need be. I did not need to use the tag spaces app to use the web clipper.
For certain types of information I would use joplin as it would store in plain text with images and I could have it accessible in different computers I have syncing joplin. It is similar to a markdown web clipper Logseq has a few plugins that are similar as well. One saves the simestamp of a youtube video which is a feature I have long needed.
I know someone who loves rightnotes web clipper or bookmarks because of how they can copy and past the clipping including a hyperink to the url, but I have not checked it out too deeply.
I also know some people who use zootsoftware for web capturing.