Is Silent Hill: Townfall a mainline game?
The publisher’s copy calls it full-length and self-contained. Outlets and Wikipedia then use two opposite labels for it. What would change this: Konami or Annapurna using either word for the game.

Who says what, closest to the studio first
The Steam page says “SILENT HILL: Townfall is a full-length, self-contained psychological horror”. Annapurna and Screen Burn carry the same sentence. Neither mainline nor spin-off appears in that copy or on the PlayStation Store page. Listed on Steam store page
He frames it by length and scope. He calls it the first full-length Silent Hill game in first person, and says The Short Message, which was also first person, was a smaller standalone experience. Neither label in dispute here appears in his answer. Said in PlayStation.Blog: the developers on the Scottish setting
Collider’s hands-on preview says “It’s the first mainline game to fully embrace a first-person perspective”. Pure Xbox calls it “the next mainline entry into the iconic horror series” in a news piece, without saying who at Konami or Screen Burn said so. Said in Collider: hands-on preview · Said in Pure Xbox: confirmed as a timed exclusive
The article’s opening sentence calls it a standalone spin-off of the franchise. That sentence carries no footnote, so the article does not say where the label comes from, and its series box files the game in the spin-off row. Said in Wikipedia: Silent Hill: Townfall
A statement that places the game inside or outside the numbered series. This is the rung that would settle the question.
Read down the ladder: the closer a source is to the studio, the less it uses either label. Collider’s line is about perspective, the first mainline game to go fully first person, which is why the first-person page covers the claim underneath it.
Where it is set, and why that does not settle it
The copy gives the game its own setting, Scotland in 1996, which is laid out on the setting page. Not found: any source tying that setting to a series rank, so it is not evidence for either label. The developer does call it a full-length game; the length figures are on the length page, and how critics scored it is on the review page, which lists scores only. The studio is on the developer page.