IANAL, so take this with a grain of salt, but from my understanding, Its legal, though it may be unenforceable. If I want to sue them, they will say I agreed to arbitration in the contract, I will ignore that and continue to file. They will counter-file that I agreed to arbitration by accepting the EULA and that the case should be dropped, I will counter-file that I only agreed to it under duress because it was either agree or throw away my TV and that the arbitration clause is invalid because of X, Y or Z. At this point either the Judge will decide to listen to arguments from both sides then make a decision or will decide based on the undisputed facts presented by both sides and will either invalidate the EULA and allow the lawsuit to continue, or will uphold the EULA and drop the case with prejudice, or will allow me to make another argument and drop the case without prejudice allowing me to re-file with a better case.

The issue is, is it worth it to spend that kind of time and money for it in the first place? If you don't have an open and shut case and can't file in a state where you can make Roku pay the legal fees, in general whatever you're trying to accomplish will cost you more than just getting off their ecosystem, which is what they are counting on. Since you would have to sue them just to see if you can sue them, it just adds extra time, money, and effort into suing them that it is more likely to deter people from actually suing and instead choosing to arbitrate under their terms which, depending on the ethical considerations of the company, could be fair or it could be heavily skewed in their favor. At which point you can decide at that point if you should sue and then will also have any evidence acquired about an unfair arbitration in the filings as well.

Either way, the legality is perfectly legal to be in an EULA, its enforceability though is mostly only backed by how much time, money, and effort it would take to bypass it. Like if there is an open door with a sign saying "Please use next door" and the next door leads to the same place as the open door. Most of us will just use the next door because its not worth the effort to deal with whatever issue might occur if we used the open door. But if the "next" door is locked, we'd just go in the open door because its no longer worth the effort to deal with procedures the company wants.