How can I choose for a object to have no shadows on it?
You can disable casting shadows in Renderer->Lighting on GameObject
I couldn’t get it to work, I don’t want it to be dark where there isn’t a light.
So it’s not about shadows but you want your object to be lit all the time.
You have to use Unlit Shader. What rendering pipeline are you using ?
Oh so I can use URP unlit.
Don’t forget about ambient lighting too: Unity - Manual: Ambient light