Integrate sensor readings saved in networked databases

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?

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.