In Common Issues we document problems which are encountered by a large part of our userbase or are very severe. They are mostly bugs, but sometimes they are notable changes which might surprise many users (example). “Broken adb” would not qualify, but “broken Firefox on a raspberry pi” would (and “no graphical output on all intel cards with the latest kernel” definitely would). The point is definitely not to reduce duplicate bugzilla bugs, it is to help people find solutions or workarounds for the most pressing issues.
I don’t want to extend the scope (with general guides on e.g. how to install multimedia codecs), because that would make the category too populated and harder to search for and find the exact issue you’re having. We have to keep the common issues list short, only limit it to the most important problems, otherwise it stops being useful. Also, mixing bugs and howtos is not a good idea.
But an easy-to-find list of howtos is definitely a good idea, in my eyes. We already have many of them in Fedora Quick Docs, but I understand that a lot of our users feel more comfortable writing the guide as a forum post, rather than submitting it as a quick doc. Also I find the Fedora Docs UI somewhat cumbersome to use.