I realise you’ve hinted at it, but also think it’s worth explicitly pointing out that it’s more about the number of users writing than just user count. It can handle concurrent readers with little bother.

For those who’ve not seen it already, there’s a good guide on when to use SQLite here: https://sqlite.org/whentouse.html

While the default is indeed to lock the entire database, it has been an option for 15 years to avoid this: https://www.sqlite.org/wal.html