Some updates:

1. Changing SteamVR to beta makes no difference
2. Occasionally, after some hard reboots, my display settings will be reset to default (refresh rate and positions)
3. I've tried uninstalling SteamVR, deleting every single VR config file, and reinstalling, still no luck

I am having a very similar issue and found no solution yet.

When launching SteamVR the computer freezes completely and requires a hard reset. Beta program or not for both the Steam client and SteamVR app changes nothing, however I have noticed that changing the Beta program participation option and "reinstalling" steam allows me most of the time to run the SteamVR app one time, after which if a close SteamVR and start it again my computer will freeze again.

I am using Manjaro with Nvidia 415.27.

I am also getting lockups but only when hitting the "home" button and opening the VR menu. It opens fine the first time, sometimes even the second, but on third open 100% it freezes the entire system.

Ubuntu 18.04.2 LTS
AMD® Fx(tm)-8350 eight-core processor × 8
GeForce GTX 1080/PCIe/SSE2
Gnome 3.28.2
OS 64-bit
Memory 11.6 GiB

nVidia driver version 418.56

up2date arch linux with i7-8700K, htc vive with a RTX 2080.
beat saber began to stutter reproducable unplayable some weeks ago where InDeath still worked perfectly.
Some days ago I kinda "fixed" it (fyi: https://steamcommunity.com/app/250820/discussions/5/1648792158831923503/#c1649919326311929210) (this issue might be unrelated, but might be good to know that it didn't work correctly already before)

now within the last 2 days SteamVR locks up the whole machine reproducable (or in fact just the screen and normal input - custom g910 hotkeys still work) and I obviously can't use VR at all.
tried both SteamVR beta and non-beta and nvidia-430.14 nvidia-vulkan-418.52.07 (usually vanilla nvidia).
nothing worked. I guess it's a nvidia drivers problem, as it also freezes with a fresh rolled out steam installation when starting the VR setup.
everything else on the system works as intended

as I also get
nvidia-modeset: ERROR: GPU:0: Idling display engine timed out: 0x0000c57e:0:0
in the logs I might have this bug
https://github.com/ValveSoftware/SteamVR-for-Linux/issues/123

me again. sorry for the noise.
I just was able to launch steamvr with xfce4 compositor disabled twice (vs multiple times in a row with gfx freeze). so pretty sure this is the problem.
for whatever reason I have xfwm4-git (4.14pre1+25+g68d5144c-1) instead of xfwm4 (4.12.5-1) installed,
so it is likely that this doesn't happen with latest stable xfwm4.
only reason I use the builtin compositor instead of compton is the zoom function btw.

last time - promised.
reverting back to xfwm4 (still no idea why git was installed shrug) did not even fix the freezes when starting steamvr with compositing enabled, but also brought back smooth beatsaber gameplay.
I hope this is no coincidence and just works as it did before from now on. good luck, people with the same problem.

I don't know if this is related, but I will leave it here anyways: https://devtalk.nvidia.com/default/topic/1051300/linux/inconsistent-but-frequent-freeze-caused-by-steamvr/3

Hello guys. In my case, I've found that disabling "Force Full Composition Pipeline" stopped the freezes!
Referencing issue #210 .

For the nvidia-modeset: ERROR: GPU:0: Idling display engine timed out error. If you are running several monitors try disabling all but one. Worked for me.

thanks @Celebratorn!
I recently switched to a Radeon VII and I'm more than happy with it, so at least for me the issue is no longer a problem :)