The schema under https://rxdb.info/quickstart.html#add-a-collection includes timestamp with format date-time, which causes this error in the console :

rxdb_plugins_validate-ajv.js?v=f67a7644:5971 Uncaught Error: unknown format "date-time" ignored in schema at path "#/properties/timestamp"

I suspect this is needed somewhere:

// ESM/TypeScript import
import Ajv from "ajv"
import addFormats from "ajv-formats"
// Node.js require:
const Ajv = require("ajv")
const addFormats = require("ajv-formats")

const ajv = new Ajv()
addFormats(ajv)