Where can I send feature requests? Both for Ubuntu as a whole and individual (supported) apps?
For individual apps, the best way is filing a bug requests or feature request in the individual applications.
Some upstream development portals might be having explicit feature for asking user ideas but most of them use their bug tracker for that.
Example, you want a new feature in
Or before filing bugs for wishlist, you might want to talk to the devs of the particular application. You can look at their mailing list or IRC channel.
You can make a feature suggest by submitting it as a "bug" at bugs.launchpad.net/ubuntu.
Mark the bug with the tag
These types of bugs unfortunately are not usually given a high priority so you may have more luck trying to approach the upstream developers.
The link to actually file a bug "Report a bug" in the top right corner leads to a page, where the possibility to file a bug is hard to find. The link can be found in the section:
It is also possible to file a bug now at the console if you type
into the console and follow the instructions.
Note: I think this whole process could be optimized and I think it is strange to call feature requests still "bugs".