Integrate sensor readings saved in networked databases

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I’ve added temperature sensors to some Raspberry Pis around my house, that feed back to HAOS using MQTT, but reliability has been patchy, especially from the Zeros.
As a backup, I’m also saving the data on each Pi in SQL databases, that I can then display/analyse using web servers on the Pis. I can add the webpage to HA, but that obviously they can’t be used as a trigger for automation.

I can’t find Scrape, but given I have control over how the data can be presented, are there any other integrations I could emulate to get the data into HAOS?

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That could do it, but then all the work is done by HA - it needs to log in to all the other devices and copy the information - rather than each of the half dozen sensors presenting the minimal information. That sounds resource heavy.
Can see how to connect to a local database, but not sure about multiple, networked connections.
Will keep looking.