That one is indeed because most of those things are opaque to qutebrowser. They're handled by the underlying QtWebEngine/Chromium, and only for a few of those things there's a way for qutebrowser to delete them. There's an issue about it here: https://github.com/qutebrowser/qutebrowser/issues/58 - but many things probably can't be done, or only in a hackish way (e.g. by qutebrowser reading/manipulating those internal Chromium files, before it starts up fully).
You can however remove ~/.cache/qutebrowser and ~/.local/share/qutebrowser/webengine/ manually.
> The ultimate goal would be some way to replace the functionality of "Temporary Containers" or alternatively "Cookie Autodelete" (you keep all the history, but everything else is in Incognito mode except for whitelisted sites.)
Via qutebrowser's `--temp-basedir` (or `--basedir`) flag, you can already start an isolated instance - but indeed the history won't be shared with the main instance (and neither will e.g. the config, but there's the --config-py flag).
There are also some "profile managers" which are based on the `--basedir` flag: https://www.reddit.com/r/qutebrowser/comments/l6zj0z/compari...
Finally, I'd indeed like to have a container-like feature integrated into qutebrowser itself in some way: https://github.com/qutebrowser/qutebrowser/issues/4102 - automatically switching containers based on the URL unfortunately won't be possible, but I think even just launching a new window with a different storage path (i.e. profile) would provide a lot of value.
> Can't disable WebRTC (= unique device id can always be tracked)
I think to fully disable it, you'll need to rebuild QtWebEngine. As far as I know, this is a Chromium limitation. Can you elaborate on "unique device id" though? I'm only aware of WebRTC leaking internal IPs, which can be prevented via the `content.webrtc_ip_handling_policy` setting.
> Great project, keep it up :)
Thanks for all the feedback, I really appreciate it!