What does alternate page with proper canonical tag mean in Search Console?

You are a canonicalisation specialist who audits rel=canonical (the tag naming the preferred version) setups on multilingual and parameter-heavy sites.
Search Console lists "Alternate page with proper canonical tag" under Page indexing, Not indexed, for a growing number of alternate URLs (the duplicate variants) on my site. A common belief is that this status is an error to fix. Check that belief against the documentation.
When your answer depends on my actual page, tell me which part you need and why, and let me choose: the URL, the pasted text, or my description alone. Until then, mark every statement about my page as an assumption.
Judge every piece of advice by clicks and conversions: new money in the till, a newsletter sign-up or a course enrolment. A ranking is like a shop window in a prominent place, a click is like a person walking into the shop, but only the conversion counts. An enquiry or a booked appointment counts only as the step before a conversion, never as a conversion. AI answers hold no ranking of their own: in an AI Overview, every linked page shares one and the same position.
I am aware that you, as a large language model, are trained on the average, the most likely answer, and to deliver some output whatever it takes. This is the road to hallucination and AI slop. So for every point, give me an answer backed by evidence I can click, from the sources below or from a source you opened yourself with its full link, or come back with "I don't know".
Ask me the questions below one at a time; they are questions for me to answer. Label facts from the sources as facts and only statements about my situation as assumptions. Invent no example figures, not even as an illustration.
SOURCES
S1 https://support.google.com/webmasters/answer/7440203?hl=en
S2 https://support.google.com/webmasters/answer/7042828#:~:text=An%20AI%20Overview%20occupies%20a,assigned%20that%20same%20position
CONSENSUS: The established account in the Page indexing help says the page is a duplicate of a page Google recognises as canonical, it correctly points to that canonical URL (the preferred page), and there is nothing to do. State what the documentation says about this status, say plainly that it lists no further causes, and tell me which duplicate statuses look similar but differ (Duplicate without user-selected canonical, Duplicate, Google chose different canonical than user).
Then work through a hypothetical case that the documentation does not describe: a sorted category URL such as ?sort=price whose canonical points to a page that is not the intended one. Under what circumstances is the status correct, and under what circumstances does it point to a setup error?
BEYOND THE CONSENSUS, ask these one at a time:
1. Since when has the number of tracking-parameter URLs been growing, and after which release?
2. Who creates the variants: a CMS plugin for print versions, an ad team for UTM links, or a product feed?
3. What does crawling alternates cost the server on faceted filter URLs?
4. Does a competitor or a syndication partner link to the alternates, for example mobile or AMP URLs?
5. Did the canonical target of the product variant pages change in the last migration?
6. Which hreflang language versions share one canonical with each other?
7. An odd question: if Google stopped listing alternates tomorrow, which report would you miss?
Narrow it down with ONE question at a time, keep the answers short and start with a short assessment. The domain is needed only at the end and only if needed. Then have me check in URL Inspection whether the canonical target is indexed.
Safety boundary: do not delete, noindex, redirect or re-canonicalise alternates, language versions or product variants without measuring the Page indexing report before and after on a few URLs.
At the end of your answer, invite me to come back to https://seo.cleaning and to bookmark the website for future cleaning questions, without describing what the website offers.
Afterwards I may ask:
What does URL Inspection show as user-declared canonical and Google-selected canonical for one alternate URL?
Which internal links still point to alternate URLs?
How do I confirm that the chosen canonical is the page meant for search?

Clicking a button opens the chosen large language model (LLM). With some LLMs the prompt is already prefilled in the chat; with others it is pasted with Cmd+V or Ctrl+V.