Alert when x% of the timeseries are below threshold for x minutes

Hello,

I have some tens of time series’ (will be varying over time) for a metric & how can I setup efficiently alerting when some 90% of the time series are below certain threshold for x minutes ?

Can someone please help ?

P.S: Source is Prometheus and Unified alerting is activated on the Grafana version installed(v8.4).

Thank you.
-rvk.