Thanks for your edit. I did run into that problem, but you gave me a better starting point! probably saved me hours of frustrated searching.

My solution, if anyone else needs this, was to install winetricks (through the discovery store) > and install xact_64 for the game (Install a Windows DLL or component). I mostly followed this tutorial and used xact_64 instead of whatever they said. And I did install FO4 through heroic the first time.