Game works like a charm on my system too.

My Specs

I can confirm it. Works fine on my Asus Vivo (Intel i5 7200U, HD620, Fedora 28)

It works for me too.
https://gist.github.com/cobblestone/f1e00a8bc66f8ca73fd8debd72d447e7

I played 11 missions so far, and everything seems to work perfectly. The only issue is that the videos in the tutorial cannot be played.

How to reproduce:

1. Launch the game
2. Click "New game", "Tutorials", "Green Beret", "Watch theory session".
3. The video will not load

Here is the log.

Here is my system information.

This happens with both Proton 3.7-8 and 3.16-6Beta.

After finishing the game, I can confirm that none of the videos are played. They are skipped and do not cause a crash, though.

Here is the output of "mediainfo H_Intro.avi":

General
Complete name : H_Intro.avi
Format : AVI
Format/Info : Audio Video Interleave
Format settings : rec
File size : 14.4 MiB
Duration : 1 min 20 s
Overall bit rate : 1 514 kb/s
Comment : Comprimido con ajustes de / Adobe Premiere 4.2: Entrelazado = 1 / Velocidad pedida = 150(CDROM) / Volver a comprimir = No / / Referencias: cada12 fotogramas / Campos = Fotograma completo /

Video
ID : 0
Format : Cinepak
Codec ID : cvid
Duration : 1 min 20 s
Bit rate : 1 222 kb/s
Width : 320 pixels
Height : 240 pixels
Display aspect ratio : 4:3
Frame rate : 12.000 FPS
Bits/(Pixel*Frame) : 1.326
Stream size : 11.7 MiB (81%)

Audio
ID : 1
Format : ADPCM
Codec ID : 2
Duration : 1 min 19 s
Bit rate mode : Constant
Bit rate : 176.4 kb/s
Channel(s) : 2 channels
Sampling rate : 22.05 kHz
Bit depth : 4 bits
Stream size : 1.70 MiB (12%)
Interleave, duration : 83 ms (1.00 video frame)
Interleave, preload duration : 734 ms

Seeing "err:quartz:GetClassMediaFile Media class not found" in the log makes me think this might be related to https://github.com/ValveSoftware/Proton/issues/1464 .

I can confirm game is playable but the videos are skipped.

Distro: Linux Mint 19.1 Tessa (64 bit)
GPU: Vega 56
Driver/LLVM version: Mesa 19.1.0-devel/9.0.0
Kernel version: 5.0.12-050012-lowlatency
Proton version: 4.2-3

media_info.txt
steam-6800.log
system_info.txt

@HonkingGoose this looks like a Quartz game with video that is: AVI, Cinepak + ADPCM

proton-4.2.9 - Crash right before main menu.

steam-6800.log
system_info.txt

I have just upgraded to Proton 4.2.9, with the same configuration as I had in the previous comment, and I can still run the game.

The game crashes before the main menu. ArchLinux, Proton5.0-9. Any updates on this issue?