Victoria Metrics is a Prometheus compatible time series database and was being used before I joined the company. I haven’t had any issues with it so I didn’t see a reason to pull it from our stack. Are you saying Timescale or Influx can natively ingest MQTT messages?
Similar to your mqtt converter you can make them ingest via Kafka or some other adapter in between. EMQX broker can directly write into TSDB but did not research into others whether they can or not.