Sorry, nobody here on the FM side of the user forum is going to check - we already know that there's no FM to ID direct path. You need to explore either exporting your content or taking it apart to save it off into formats that ID can import.
Well, "no FM to ID direct path" is not entirely true. There is the DTP Tools plugin which could at least be tested, although they do NOT support equations. It seems a little bit outdated (officially supporting ID up to CS6 and FM8 MIFs), though. However, I've successfully transferred some FrameMaker content to ID this way, even with later MIF versions.
There is no equation editor in InDesign. There are a few plug-ins that will do the equation work in InDesign.
I've done the conversion by exporting the Frame file to *.rtf and then placing it into InDesign. All of the equations will export/import as graphics which you can use as a guide to recreate the equations in InDesign.
What version of FM?
And using the native Frame equation editor, or MathFlow (MathML, a form of XML)?
Based on a quick search, it appears that ID doesn't support generic XML import, but even if if did, you'd still be exporting or rendering the page(s) from FM, and then importing them in some format that ID does support.
Something that supports text and vector art would be ideal. With XML off the table, SVG and EPS or PDF might be next on the list, except course, that SVG is also XML.
When you save a FrameMaker document as XML, you can set the read/write rules to export equations as MIF. You can then use the following utility to batch-convert them from MIF to MathML:
Another (more sluggish, but perhaps more robust) method is converting the Equations in FrameMaker to LaTeX equations using MathPix, from there use tex2svg https://github.com/mathjax/mathjax-node-cli/blob/master/bin/tex2svg
This is a good method if you have less than 50 ish equations, but it would be very tedious to do for many equations.
Personally, I created a CSV file that contained the LaTeX equations and a filename.svg from all my documents. I then ran a batch process of tex2svg over the rows in my CSV, then reimported the .svgs into the file
This may not be a solution for you, as I do not know how Framemaker to InDesign handles SVG graphics, but it is an interesting workflow regardless.