Bloaty seems to be what I was looking for. It's limited, requires symbols for some options and doesn't have GUI but is a start. Probably someone already made GUI for it and I just need to search.

Thank you both.

I noticed that https://www.jackyoustra.com/binary appears to fail with 'Reference Error: Can't find variable: SharedArrayBuffer' on Safari when you give it a binary.

On Firefox, it does not display the size of sections unless you hover the cursor. Not sure if it's intended - just noting here.