SQLite comes up a lot on HN, but it's not PR - it's content that others find interesting, myself included. In most cases it's not even official SQLite content being posted, but rather other projects or blogs around it.
If anything, SQLite deserves _more_ PR. It's a fantastic piece of software, and at my company we use it _a lot_; mostly for testing, but also for some micro-services where data amount is small-ish, and almost never change (postal codes, country data etc.)
I hate it when I see .NET Core tutorials (as an example) where they fire up MSSQL in EF just for tiny amounts of data, and then using a bloated DB-viewer GUI to show what's in the database, instead of just going to the CLI asking SQLite "directly."
SQLite works pretty great for managing larger or more dynamic datasets, too; it’s just where concurrent access begins to increase that it stops being appropriate.
As far as I can tell the SQLite team's main PR strategy is consistently and quietly releasing software that's so good that large numbers of people do PR for them, for free.