I confirm you can’t change the headset refresh rate with linux_v1.14 unless you toggle VR mode. In addition, it fails sometimes to display the Steam overlay (clicking the Index HMD button or using the Knuckles button), and I’ve had occasions where the SteamVR monitor didn’t display either (this is the little window showing the connection state of the HMD, controllers, LH stations). Otherwise I agree it is the best SteamVR for simulation and I agree not just for FS2020.
Speaking of refresh rate, I now find using Index at 120Hz + SteamVR linux_1.14 + NVidia 457.30 giving the best overall experience. More details about all this and more here:
My 2070 SUPER VR settings and suggestions (Valve Index)
NB: @Mendigo1151 is reporting trying an older NVidia Driver giving even better results on his system than 457.30. I didn’t try it yet (tried many others) but I’ll do soon: