Outcome from 2018 SEO project with Go Fish Digital:
There are a lot of non-mobile links (i.e. https://en.wikipedia.org) on our mobile pages (https://en.m.wikipedia.org). When the user clicks on these non-mobile links, they get redirected to the mobile version, and search engine crawlers will experience the same thing. Redirects like this aren't great for users, and they're also bad for crawlers because it slows the crawling down and might cause it to miss pages. These links on the mobile site should be directly to the mobile site instead.