There is probably no fixed minimum at all. By Google’s account, a page only needs to be reachable, linked from a page Google already knows or listed in a sitemap, for it to be crawled. A lone internal link, or one sitemap entry, can be enough to get an orphan page discovered and into the crawl queue. So the truthful framing is that “minimum links to index” is the wrong frame; the real question is whether the page is reachable at all, and then whether it is reachable strongly enough to be treated as worth indexing.
That distinction is the step most “how to get indexed” advice skips. Discovery and indexing are two different events. One link or a sitemap gets the page discovered. Whether it then gets indexed depends on the page clearing Google’s value threshold, which links alone do not guarantee. A page can be perfectly reachable and still sit unindexed because nothing about it earned a place in the index.
Where link count does matter is as a practical floor, not a hard rule. A page with only a sitemap entry and no internal links pointing to it is a candidate for getting stuck in “Discovered, currently not indexed,” because thin internal linking signals low priority and Google may keep deprioritizing the crawl. Enough contextual internal links that the page is clearly part of your site, reached from relevant existing pages rather than stranded, is what moves it from technically reachable to worth crawling and keeping. There is no published number for that; treat it as working practice and watch how your own new pages behave in Search Console.
Before you expect a new page to index, check that it is not orphaned: confirm at least one or two relevant pages link to it in context, and that it sits in your sitemap. That clears the discovery step. If it still does not index after that, the problem has moved from reachability to value, and more links will not be the fix.