Greetings! Is there any way to use existing prometheus storage (or VictoriaMetrics) to gather mertircs via query-service?

No, what’s the usecase? You can configure the collector to scrape targets though.

Saw this one - https://signoz.io/docs/faqs/product/#is-prometheus-included-in-signoz and thought that the service supports remote_read from existing prom stack. Is it possible? This will be useful to not duplicate data (metrics) in both CH and Prometheus.

I don’t think we support remote_read now.