This still works. After starting a trial the discount does indeed begin at 25%, but steadily increases to 50% in the last few days of your trial.

Plus, even if you don't cancel the trial and let the normal full monthly pricing kick in, during that entire first paying month (i.e. your second month on TradingView) they will still let you sign up for the 50% off plan, with that first monthly payment you already made counting towards the discounted annual plan - you just need to pay the difference.