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Set it manually on where it lives best, or programmatically let them pick the one that is most relevant. I would not implement any logic based on where users are coming from. You're likely well of by spending your engineering resources better than doing that for SEO.

You should use a canonical for pages with  this utm - but the canonical is without utm. Otherwise you have a chance that you earn duplicate content (you mentioned utms in SERPs).  It doesn't make sense to use a canonical with utm, because this would make organic users to utm=gmb users (if indexed and clicked). And if you dont use canonical and link internally without utm? It happens, that people click on the found knowledge panel url and link to it - bamm! indexed and you cant trust your utm anymore and again, duplicate content. Use canonical = yes  include utm = no your pages: https://yourpage.com/subpage https://yourpage.com/subpage?_utm_source=gmb_ should both have this canonical: <link rel="canonical" href="yourpage.com/subpage"> ```

Great! Happy to help

Just so you know Meta no-index can be applied through the HTML but also through the HTTP header which might make it easier to implement on such a highly generated website

Hmmm. This is tricky. Some ideas - hope something here is helpful: Have you tried "inspect URL" in search console? That has information about canonical selections these days and may be helpful Are the canonical URLs (and no parameter URLs) included in the XML sitemap? Might be worth trying cleaning that up if there is any confusion Cookies could work - but it sounds to me as though that would go against your client preferences as the non-cookie version would have to remove / work without parameters I think - which you indicated they weren't prepared to do Failing all of that, what about picking one category to be the primary category for each product and canonicalising to that (which will have internal links) instead of to the version with no parameters? Could that work? Might nudge towards the canonical being respected

I posted a bit of a Reddit rant here under my personal SEO alias of "studiumcirclus": https://www.reddit.com/r/SEO/comments/bgqelg/changing_web_host_will_it_affect_google_rank/em1m0cg/?context=3 (click "View Entire Discussion") Mainly these things vex me about the platform: "In basic terms, Shopify is limited by its vision. They want to make sites easy to design for the average-joe, which means they have to spend most of their platform dev time on the back-end of the system and not the front-end of the sites which it produces _ If they're always bogged down making extra tick-boxes to change things in the back-end, how can they be keeping up with cutting edge SEO? With WordPress you have a much larger dev community making add-ons, many of them completely free and still very effective. Because everyone is on WP, when new Google features, directives or initiatives come out they are quickly embraced (putting all sites on WP one step ahead)_ _ With smaller dev communities, platforms like Shopify or Magento lag behind. Why do people always expect that 'average' will rank 'well'? Ahead of the curve ranks well, average ranks averagely_ _ Also Shopify has some nasty Page-Speed issues which they won't acknowledge and they just argue about instead of fixing things. It's just not good for SEO_" Other "Shopify is bad" evidence: https://moz.com/community/q/main-menu-duplication#reply_391855 - just contains some of my thoughts on why Shopify isn't that good https://moz.com/community/q/site-crawl-status-code-430 - a relatively recent problem someone had with their Shopify site, scroll down to see my reply https://moz.com/community/q/duplicate-content-in-shopify-subsequent-pages-in-collections - someone else having tech issues with their Shopify site. While my answer was probably right, they probably couldn't implement the fixes

Thanks for confirming my thoughts. Some of these page _do _rank, but either for seemingly irrelevant terms or for terms that also rank the main lander page. Also, after checking the analytics, they drive almost no traffic.

This was an issue that yoast came up with on an upgrade with wordpress in the middle of 2018. It may be worth a little research into how their "purge" plugin worked as it did exactly this. Using the htaccess file simply tell google not to index the resource pages then they will naturally over time fall out of the search  or you can purge by Log into the Google Search Console and select the desired website. Click on “Optimization” in the left-hand navigation. Click on “Remove URL” in the sub-menu. Click on the button “create a new request for removal” on this page. Once this is done and they are set to no index. Problem solved.