You could do an ad different from your post with the same content, but I guess you don’t want that.
You could also let the post run for 1-2 weeks to gain as much organic traffic as possible, and then start to boost / promote it to get paid traffic after. You could edit the link when you convert it to a paid promotion.
The only other method I can think of:
1. Create a regular FB post without an action button. You can put a link with organic UTM parameters in the text if you want, optional
2. Create an ad to use this post, but add an action button *in the ad* (not the original post) that links to the paid UTM params you want to use.
I think the problem is that this will add the button to the original post as well, IIRC