Will try karakeep.
Although, to be fair, running it in Docker seems less fraught and breaks less often (and it's a lot easier to restart when it does break.)
(I've got a pipeline from Instapaper -> {IFTTT -> {Pinboard -> Linkhut, Dropbox, Webhook -> ArchiveBox}} which works well most of the time for archiving random pages. Used to be Pocket until Mozilla decided to be evil.)
I've been using an extension called WebScrapBook to locally save copies of interesting webpages. I use the basic functionality, but it comes with tons of options and settings.
I would look into what happened with the single file copies you made that didn't work because that is highly unusual.
Edit: What's the best way to support the project? I'm seeing there's an option through the Mozilla store and through GitHub. Is there's a preference?