Hello!
This is exactly why we don’t implement nonstandard stuff like that — because you’ll lose it.
TSF has no methods built-in to affect your post-content (like this feature) because we’re against vendor lock-in.
So, I’m afraid you’ll have to resort to other means, such as installing Gutenberg Block Editor Toolkit. That Toolkit gives you back the option, but it won’t read Rank Math’s values; you must install and have active Rank Math to get those nofollow attributes back.
There’s also an ongoing discussion on bringing this feature natively to WordPress, which I wholeheartedly support: https://github.com/WordPress/gutenberg/issues/23011.
Lastly, we also have an issue open about this, right here: https://github.com/sybrew/the-seo-framework/issues/568.
I hope this covers everything, and I hope the plugin linked helps you along!