I've researched everything that only requires the automation science pack, and in the tech tree everything is green and researched before the belt sorter. It still states unable to research due to unfullfilled prerequisits.

OK, so py is missing the "electronics" tech. /c game.player.force.technologies['electronics'].researched=true fixed the issue for me.

Autor! Please change data-updates.lua, add this:
data.raw.technology["belt-sorter1"].prerequisites = {
"vacuum-tube-electronics",
"logistics"
}