https://mods.factorio.com/mod/hot-metals

When using both of these I'm experiencing a problem where pipes are not placeable by bots anymore, as it somehow changes the placed ghosts to become hot pipes from the hot metals mod, instead of regular pipes. Disabling this mod fixes the issue.

More details here:
https://mods.factorio.com/mod/hot-metals/discussion/689916f147e3e06cd25d9899

I don't know if that's a solution, but when I disabled the startup settings in Flow Control ("New subgroup for pipe items" and "Picked up pipes become base pipes"), the placement of ghost pipes seems to work again... Not sure if for all cases, just the first few quick tests.

I don't know how these two mods interact, I think it's a bit subtle since I couldn't figure out by looking at their sources why this behaviour arises, but maybe disabling those settings fix it...

Well I ended up uninstalling this mod in favor of Flow Config (https://mods.factorio.com/mod/flow-config) which I find nicer to use.

oh nice, will have a look, thanks! :-)