...I was brought to this site by clicking the "Feedback"-link on the bottom of an askubuntu.com question page, meaning that I did so because I had something to tell. When coming to the site though, it looked like was yet again about getting support ("aks question"). Maybe you think I'm hairsplitting, but I do think that, if this is the place where feedback is supposed to go, it need not necessarily be a question. So being asked to make it a question, I feel a bit like I'm being patronized.
Meta, like main, is organized into "questions" and "answers." We speak of someone's "question" on meta even if it does not ask a question per se (like this one, for example).
Many questions and answers on meta are actually asking questions and giving answers. But for those that are not, those are still the site-specific (or actually, Stack Exchange network specific) technical terms that we use.
Someone who is confused about this or any other aspect of how meta or the main site works can ask a question about it here on meta. It's necessary that it be clear how people can ask questions here. Provided that this is clear, the how of any other activity can be asked about. Therefore, there is minimal to zero negative impact associated with the possible confusion between question in the site-related technical sense, and actual questions.
Furthermore, if meta looked and felt too different from the main site, then it would be more confusing, there would be more to learn, and people would find it difficult to use meta to get help.
So: You are right that feedback need not consist of or include any questions. And such feedback is still welcome here on meta. (In contrast, posting a "question" on the main site that is not really asking a question would result in that question being closed, usually as not a real question.)
In conclusion, the Ask question link near the upper-right corner of any page, and other interface elements that refer to asking questions, use that language for consistency with the main site, because question and answer are used as technical terms on the site, and because it's especially important that meta be accessible to people who are using it to ask a question. But you may feel free to post a "question" on meta that gives feedback about the site without actually asking anything. Often, you may find that asking people things fosters discussion, but it is not the only way to foster discussion and posts on meta are not required to be "real questions."
Some kinds of feedback aren't for meta, though.
The main thing is that if the feedback is about the site, it's generally good for meta. If the feedback is not about the site itself, then it's outside the scope of meta.
I recommend reading the meta FAQ if you have not done so already (especially if you plan to post something that is not a question). The meta FAQ has the shortcoming that it too refers specifically to questions, but it should still give you an idea of what sort of posts are considered on-topic and constructive on meta.
To expand on that, here are some examples of kinds of feedback that are generally not appropriate on meta because they are covered by other features of the main site and (usually) constitute feedback that is not really about the site itself.
If a post should be edited, click the edit link and submit the edit. It will be reviewed, and if it is accepted, it will be applied.
If someone has answered one of your questions and you want to give feedback to the author of the answer, post a comment on the answer.
If you find you cannot, make sure you are logged in with the same user account that you used to post the question. If you have multiple accounts, then so long as at least one of them is registered, you can get them merged into one single account by clicking the contact us link at the bottom of any page and requesting the merge.
If you think a question is clear and well researched, or unclear and poorly researched, or that an answer is good or bad, vote it up or down. If you have constructive criticism for a question or answer, comment on it. (You can always comment on answers to your own questions but you need 50 reputation to comment on other posts.)
If you don't have enough reputation to vote and/or comment yet, you should still not generally post on meta. Only if you think you've identified an issue that affects the site or Ask Ubuntu community as a whole in a significant way, or if you want to talk about the site itself (as opposed to the subject of the site, Ubuntu) should you post on meta when posting a comment would usually be sufficient.
If you see a problem, like spam or an answer on main that is not really an attempt to answer the question at all, flag the post. You have over 15 reputation, so you can flag any post or comment.