I enabled onboard audio, took my case apart to remove the soundcard and uninstalled all drivers of the card.
Now LFS and R3E work.
However, Assetto Corsa, Rfactor 2, GSCE, older simbin titles, Project Cars, ORC, Witcher 3, Arma 3, Portal 2, DayZ, Miscreated, Amnesia, Penumbra, Stalker, Red Orchestra 2, Killing Floor 2, Next Car Game: Wreckfest, Kerbal Space Program, Insurgency, The Forest, BeamNG, Alien: Isolation and Rust all work with the sound card.
Is the card or devs in the blame here?
I can't see myself going through this process just to play these two games, especially when the sound card is actually a big improvement over my onboard.
Agh!