Those who claim that "removing the app from the platform is not censorship because the company is a private company" do not understand how censorship works, nor what it means.
Of course it's censorship. In this respect, the global West does precisely what it criticizes in Russia or China. I bought a Roku box because I thought that, as an independent (relative to the behemoths that are Google, Apple or Amazon), they would be more... independent! I was wrong.
Probably the best course of action at this point is to install Kodi on a Raspberry Pi or buy one preinstalled, and watch RT there (besides the good suggestions of casting RT). We're lucky the open-source world is decentralized and cannot be controlled by governments or a bunch of shareholders.
This does not alleviate the shame that's cast on Roku and their idiotic decision to reduce the platform's diversity, freedom of speech and equal chance of expression for the benefit of an oligarchy and Western thought police.
No, you are confused about the meaning of censorship. To quote Britannica:
censorship, the changing or the suppression or prohibition of speech or writing that is deemed subversive of the common good. It occurs in all manifestations of authority to some degree, but in modern times it has been of special importance in its relation to government and the rule of law.
Note the last part, it is in relation to government. Roku is not the government, they are a private company in a free republic. The have every right to determine what content they will permit on the hardware they sell because of the terms of service they apply equally to all providers. None of us knows the details why, but RT is not complying with those terms of service, so they were removed. Not allowing a provider onto the Roku platform is not censorship, because RT is still able to issue their content through other means. They are not being "suppressed" for overall access. They simply aren't allowed on a certain platform. No, that is not censorship.
Considering Meta has now has banned Russian state media broadcaster RT and other Kremlin-controlled networks, alleging the outlets have engaged in deceptive influence operations and attempted to evade detection, it's highly unlikely other outlets will continue providing them a US audience. Meta owns Facebook and Instagram, two platforms that have had major issues with false information sharing from the Russian broadcasters, and if they won't let them on it's a pretty good bet few others will permit it.
Time to donate the Roku and get an android box
Still available via the Rumble channel/app or Odysee for your Roku device
https://channelstore.roku.com/details/9d7828c984f24d379ee54f2f2028361f/rumble
https://channelstore.roku.com/search/odysee
Or you can go their website https://www.rt.com/on-air/ and either cast it through your Roku or use an HDMI cable.
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Every streaming device/platform is going to have its shortcomings and leanings. Can either throw them all out, build your own, or find a way around it.