It is possible to see in some place any more doc of this mod? I cannot make work the game.forces.player.get_entity_count function.
The web https://statorio.chksm.net/ is down all the time.

Yes unzip the mod for a README.md with some more examples. For you these look relevant:

game.forces.player.get_entity_count.gun-turret - Turrets deployed by the vanilla player force
game.forces.*.get_entity_count.transport-belt - Transport belts deployed for all forces
game.forces.*.get_entity_count.stone-furnace - Total number of stone furnaces for each force

Or maybe:

game.forces.player.entity_build_count_statistics.input_counts.stone-furnace - Stone furnaces produced
game.forces.player.entity_build_count_statistics.output_counts.stone-furnace - Stone furnaces consumed

It tests okay with latest Factorio /stat test game.forces.player.get_entity_count.gun-turret

My hobby server was unavailable for 4 months, rebuilding is work in progress. Thanks for reminding me to include Statorio, for now I have removed the homepage link.

Oh also, for help with the Factorio API entity names, there are some hints in this mod's FAQ, or the official Data.raw has a complete list

Thanks a lot!!!
The problem was that I cannot access Nullius mod objects with get_entity_count, I dunno why, because with item_production_statistics.get_flow_count works fine with all Nullius objects.
It works fine with vanilla objects. Thanks again.