Another user who chooses to go by the name of "TOASTER" and I have written a parser in python with the purpose of parsing through the text files contained in NASR subscriptions freely available from the FAA and writing the necessary data into dat files that flightgear can use. We've uploaded the code to a github repository, and I'm looking to tell other users about it.
This actually came about because I was looking for updated navdata and didn't want to pay for navigraph. I inquired on the FlightGear discord server, and TOASTER was kind enough to let me use a python script he/she had written for parsing fixes. After that I went on to try and write one for navaids, and TOASTER ended up joining me and providing a great deal of assistance since I didn't know python very well. We ended up with 3 python scripts, the original one for fixes, one for navaids, and one for airways. This aims to be an easy method to get up to date navdata for free, without paying for a navigraph subscription.
The parser project is available on github:
https://github.com/SkyClan480/Flightgear-Navdata-Parser