This solved it for me!

I added:
local resource_autoplace = require("resource-autoplace")
data.raw.planet.nauvis.map_gen_settings.autoplace_controls["geothermal-vent"] = {}
data.raw.planet.nauvis.map_gen_settings.autoplace_settings.entity.settings["geothermal-vent"] = {}
To the top of the ...

To create my first mod, I've chosen to update/migrate an existing (older) mod from 1.1 to 2.0: https://mods.factorio.com/mod/geothermalpower-yalda

I've managed to update the code to "run", but the resources (geothermal vents) do not place during a new game map gen, and does not show in preview.

I ...