Terra Palus 0.2.8 crashes the game at startup on Factorio 2.1.20 (2.1.x changed several prototype property types). Three separate issues, all in prototype definitions:

1. prototypes/item/items.lua — palusium-ore uses the removed singular property: "Error while loading item prototype "palusium-ore" (item): ItemPrototype::fuel_category was removed. Please use ItemPrototype::fuel_categories." Fix: fuel_categories = {"chemical"} (note fuel_categories takes a LIST of category names, not a string or a dict/set).

2. prototypes/recipe/recipes.lua — palusium-refining, palusium-liquefaction and one more recipe use categories = "chemistry" (a string). The plural categories key must be an array: "Recipe palusium-refining has malformed categories: it should be an array of strings but string was found". Fix: categories = {"chemistry"}.

3. prototypes/planet/planet-terrapalus-map-gen.lua and prototypes/autoplace-controls.lua — the opposite mistake: category = {"enemy"} / category = {"resource"} on autoplace-control prototypes. AutoplaceControl::category is still a plain string: "Error while loading autoplace-control prototype "gleba-spawner" (autoplace-control): Value must be a string in property tree at ROOT.autoplace-control.gleba-spawner.category". Fix: category = "enemy" / category = "resource".

4. data-updates.lua — the PlanetsLib orbit sprite declares sprite_size = 500 but graphics/terrapalus-orbit.png is 387x387: "The given sprite rectangle (left_top=0x0, right_bottom=500x500) is outside the actual sprite size (left_top=0x0, right_bottom=387x387).: terrapalus/graphics/terrapalus-orbit.png". Fix: sprite_size = 387 (or ship a 500x500 png).

After applying these fixes (all four) locally, the mod loads cleanly alongside a large modpack on 2.1.20. Happy to share the patched files if useful. Thanks for the mod!

Thanks for the detailed report! Terra Palus runs on 2.1 in my updated version: https://mods.factorio.com/mod/terrapalus-updated