We just tested my project on my brother’s computer and the same errors during migrating (screenshot in the question post) showed up as on my computer. And we somehow resolved the problem of rendering sprites - my brother simply reset the material of the sprite to default. I had no idea you need a material for sprite to be visible? Anyway, that’s a big relief that I understand now what was causing the problem. The problem of migrating… there is one hint. In my Content I used the name “Impulse” for a folder, which is the same as the project name. After my brother changed the name for any different - the errors disappeared. I hope at least that was the case.
For now, I still have no idea why the default material didn’t want to migrate with the rest of a sprite. Especially after solving both issues. Anyway, I will test it tomorrow.