In sandbox, I attempted to test the Inlaid Lamp Extended mod but received this error when attempting to place either of the Inlaid Lamp entities.

The mod Flat Solar Panels (0.1.12) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Flat-Solar::on_built_entity (ID 6)
Unknown entity name: flat-lamp_
stack traceback:
[C]: in function 'create_entity'
Flat-Solar/control.lua:35: in function 'gizmatizePanel'
Flat-Solar/control.lua:11: in function <Flat-Solar/control.lua:3>

In control.lua modifying line #164 from "flat-" to "flat-solar" resolves the issue. The same string is used in two other places in the file, and probably should be changed, but not required to resolve this error.

It struck me as odd that an entity that was not a solar-panel would reach that point in the code. When I logged the name and type of entities being tested at that point in the code... I am not sure the solar-panel test above is returning false as expected.

Yeah, I see the problem. I'll work on a fix. I just prefixed "flat-" to solar panel entities, and confirmed that they are of "solar-panel" type, but that's clearly not unique enough.

Latest version has a fix for this.

Yes, the new version is working fine now, thank you!