Started setting up recycler loops on Fulgora, Concrete being a potential source of Stone Bricks with byproduct of Iron Ore. At the moment I can filter out instead by Stone Brick, so not stuck or anything.

Huh, that's odd. There's a setting "Show all items in selection lists" in the Interface settings, so you can use that, but I have no idea why ore doesn't show up there. I'll take a closer look after work and see why that is, the game might be doing something weird with the available items, since I haven't touched anything regarding ore or splitters.

I spent some time looking at it and came to the conclusion that the game is auto calculating what things to show in the filters based off of what recipes you have available at the start and what resources you can get from mining things on the surfaces you have available to you. Iron ore isn't on this list because you can't "craft" it and you can't mine it, and because Nauvis is locked at the start it doesn't see iron ore as being available from there either. I don't know if I can do anything about this without having a really, really janky solution, but I'll try to see if the devs can fix this on the engine side because it should be taking recycling recipes into account when populating the list anyway, especially for other mods with custom hidden recipes.

I may have found a small workaround, if you delete the mod and reload the save you will have the ores available for filtering. Not sure of any bugs this may cause down the road, but this did fix it for me.