Your phrase is somewhat contradictory… Selling point is security, at least do it right. Even for the free plan. If it was free, it wouldn’t be sold. But I get your point.
Do you really need a strong key for your TLS? If your website runs a business that needs a stronger encryption, then you’ll not survive much by wanting everything for free.
And let’s not forget that Cloudflare offers post-quantum encryption for free for browsers that support it.
And if you’re just trying to get a better score on this tool, stop wasting your time. One of the things I see is new webmasters going crazy wanting to get the best score on a bunch of tools and forgetting the main focus.