The result of the discussion was: delete. ♠PMC♠ (talk) 20:39, 31 May 2019 (UTC)
Static micro-portal with no selection or rotation of content. Abandoned since creation in 2008, redundant to head articles and navbox.
Created[1] in January 2006 by Sylvain1972 (talk · contribs).
The list of sub-pages at Special:PrefixIndex/Portal:Tibetan Buddhism shows a slim set, with just one of everything:
WP:POG#How_often_to_update? says that unless automated, the content selection should be updated monthly, or preferably weekly. Even on a monthly cycle, this pseudo-portal has missed over 130 consecutive updates.
There is a theoretical case for arguing that this is a broad topic. But in practice, it has not met the WP:POG requirement that portals should be about "broad subject areas, which are likely to attract large numbers of interested readers and portal maintainers". It has consistently failed to attract maintainers, and in Jan–Feb 2019 it got only 11 pageviews per day, which is less than the abysmal median of 13 per day for all portals, and only 1.3% of the 779 daily views of the head article.
Per WP:PORTAL, "Portals serve as enhanced 'Main Pages' for specific broad subjects". But this is massively less useful in every respect than the head article Tibetan Buddhism and its sidebar Template:Tibetan Buddhism sidebar and navbox Template:TibetanBuddhism.
Two newish features of the Wikimedia software means that the article and navbox offers all the functionality which portals like this set out to offer. Both features are available only to ordinary readers who are not logged in, but you can test them without logging out by right-clicking on a link, and the select "open in private window" (in Firefox) or "open in incognito window" (Chrome).
Similar features have been available since 2015 to users of Wikipedia's Android app.
That sets a high bar for any would-be-portal-builder to vault if they try to satisfy the WP:PORTAL principle that "Portals serve as enhanced 'Main Pages' for specific broad subjects". It would take a lot of work to make a portal which genuinely offers more than the head article Tibetan Buddhism and its sidebar Template:Tibetan Buddhism sidebar and navbox Template:TibetanBuddhism.
But maybe someone will find a way to make such a better portal, and a team of editors to maintain it ... so I propose that this portal and its sub-pages be deleted per WP:TNT, without prejudice to recreating a curated portal in accordance with whatever criteria the community may have agreed at that time. BrownHairedGirl (talk) • (contribs) 02:37, 24 May 2019 (UTC)