litefs and litestream are interesting, but they all continue to not support confirmation that a transaction is durably replicated OR that failover won’t cause data loss. until that point it just seems like a sequence of experiments.
However, I disagree that it's just a "sequence of experiments". There are a lot of applications that can benefit from asynchronous replication. Synchronous acknowledgement of writes can impose a high cost on throughput so many folks use async replication, even in systems like Postgres.
SQLite is unfortunately (?) kind of hard to modify for external processes and while it's built very extensibly it's often not the thing you can kind of just... turn on, if that makes sense, and SQLite lives in the address space of the executing program.
You end up with stuff like hacking LD_PRELOAD[0].
Note: Litestream (Ben) was acquihired essentially by Fly.io (so that should explain all their recent SQLite content!).