Prometheus integration does not differentiate between "unavailable" and "unknown" entity states

[K900]

The problem

As currently written, the Prometheus integration reports entities as "unavailable" when they're either actually unavailable or in an "unknown" state:

core/homeassistant/components/prometheus/__init__.py

Line 83 in 79dbc70

IGNORED_STATES = frozenset({STATE_UNAVAILABLE, STATE_UNKNOWN})

This makes it really hard to set up an alert rule that would trigger on things actually being unavailable, as many integrations don't report states for things such as action buttons, and thus those are always in the "unknown" state.

It would be nice to have a way to differentiate those two cases on the Prometheus side, instead of having to hardcode a list of known-unknown-state entities.

What version of Home Assistant Core has the issue?

2025.2.5

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant Core

Integration causing the issue

Prometheus

Link to integration documentation on our website

https://www.home-assistant.io/integrations/prometheus/

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Additional information

No response

[home-assistant]

Hey there @knyar, mind taking a look at this issue as it has been labeled with an integration (prometheus) you are listed as a code owner for? Thanks!

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