There is FerretDB v1, which provides MongoDB protocol for SQLite. See https://github.com/FerretDB/FerretDB/tree/main-v1
From https://docs.ferretdb.io/migration/migrating-from-v1
> Unlike v1.x that provides options for PostgreSQL and SQLite as backend, FerretDB v2.x requires a PostgreSQL with DocumentDB extension as the backend