If you want change you got to direct your comments to the HDMI forum. Here we can talk about it forever and if they never see anything they won't change. I sent the following email to: admin@hdmiforum.org

Dear HDMI Forum,

I was recently saw the news that the HDMI forum was blocking open source implementations of the HDMI 2.1 specifications and I want to express that I really believe this is a bad idea. I hope the HDMI Forum will consider allowing it. I can't say I understand what the concern is or the reason for blocking it but I really doubt that whatever issue is envisioned will actually come to fruition, instead I believe that allowing open source implementations will be beneficial for adoption of the standard and since if I understand correctly the licensing fees are based on hardware sold so having open source code will of course not exempt anyone from HDMI licensing rules.

Thank you so much for your consideration,

(Name)

Maybe it's not perfect (I already wished I worded one sentence better) but I think what matters most is just trying your best and using your voice whenever you can. Be sure to send your email too, the more they receive hopefully the higher the chances that this works but of course be sure to use your own wording, I just put that here for an example.