Rakuten TV blocks Linux

A question about Linux blocks on streaming sites. Is there a way to go around them?

For example, Rakuten TV has some free movies that are viewable around here. I could watch them on Windows but after the Linux switch can no longer play them. The site specifically tells me that GNU/Linux is not supported.

I don't understand what the problem is to support Linux from a technical point of view.

Would some spoofed client header be enough here?

https://www.rakuten.tv/