As of my last update in January 2022, there hasn't been any widely reported statement or confirmation from Prithviraj Sukumaran stating that he doesn't take remuneration for films. However, it's not uncommon for actors, especially those who are passionate about their craft or financially secure, to take on projects without upfront payment or for reduced fees, particularly if they believe in the project or want to support a particular cause.
Regarding Akshay Kumar, while there have been reports and rumors suggesting that he often takes a share in the profits of his films rather than a fixed salary, there hasn't been official confirmation from him either about completely forgoing remuneration. Like Prithviraj Sukumaran, Kumar's reasons for such a strategy, if true, could include a variety of factors such as passion for certain projects, belief in profit-sharing models, or other personal reasons.
It's worth noting that the financial arrangements between actors and filmmakers can vary widely and are often subject to confidentiality agreements, so definitive statements about their payment strategies may not always be readily available to the public.