I had to program an FT857d that I picked up, but my "current" memories were in my ftm-500 which I used the rt systems file to program (on my mac). First thing I did was export CSV, but then chirp wouldn't import. Started looking around and there wasn't any utility to do this, bummer. Everyone was just cutting/pasting between two spreadsheets and modifying columns. Looking at the outputs, you just need to map some columns and change some column names. So I whipped up a little script that will take an input file from rtsystems and output csv that will directly import into chirp. It does require python 3.10 or newer to run as it uses match/case rather than an endless set of if/elif/else.
Hope people find it useful, I did see a thread where someone was already having the same problem I was.