Can the DNS entry be changed?
Then you could fake DE via smartdnsproxy.com and then the Prime Video app should also run.
According to https://support.smartdnsproxy.com/article/80-amazon-fire-tv-dns-setup-for-smart-dns-proxy it should work, but I want to make sure before buying that this also applies to the (newer) 4k variant.

Question

Can the DNS entry be changed? 
Then you could fake DE via smartdnsproxy.com and then the Prime Video app should also run.
According to https://support.smartdnsproxy.com/article/80-amazon-fire-tv-dns-setup-for-smart-dns-proxy it should work, but I want to make sure before buying that this also applies to the (newer) 4k variant.

Answer

Yes it works the same with both devices

Answer

Change The DNS On Your Fire TV (Only to setup your Fire TV

https://support.smartdnsproxy.com/article/80-amazon-fire-tv-dns-setup-for-smart-dns-proxy

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