@ffm2 I assume Arch has the latest Blender which deprecated (removed?) the DAE import and export because they no longer wanna support this. This means 0 A.D. is probably the last big open source project to use the Collada format. I haven't checked if the settings allows you to restore it;
Doing a bit of 3D printing myself, NIFA is right, unless you get a way to get the normal map details from the textures, your models will look very bland, and they clearly are not meant for printing, because of their non manifold nature.
The Vulkan renderer is on by default, for the shaders, you can either compile them yourself (which is a bit annoying) or you can use the script to download the current built ones https://gitea.wildfiregames.com/0ad/0ad/src/branch/main/source/tools/spirv/get-nightly-shaders.sh (on Linux)