Since these games are on sale I just bought the trilogy pack. I will try out the mfplat fixes on this one in a few hours.
Edit: mfplat install like in RE2 doesn't work in this game either.
The game's opening video file (english version) has the following encoding:

Audio #1
albumart                  : false
audio-channels            : 2
codec                     : wmav2
decoder-desc              : wmav2 (Windows Media Audio 2)
default                   : false
demux-channel-count       : 2
demux-samplerate          : 48000
dependent                 : false
external                  : false
ff-index                  : 0
forced                    : false
id                        : 1
lang                      : jpn
src-id                    : 0
type                      : audio

Video #1
albumart                  : false
codec                     : wmv3
decoder-desc              : wmv3 (Windows Media Video 9)
default                   : false
demux-fps                 : 29.97002997002997
demux-h                   : 1080
demux-w                   : 1920
dependent                 : false
external                  : false
ff-index                  : 1
forced                    : false
id                        : 1
lang                      : jpn
src-id                    : 0
type                      : video

#3163
See my update for the whole trilogy pack as the games are now fully playable with staging proton builds. (at least appear to be fully playable, now we need to test them :-) )

Atelier Arland series Deluxe Pack - アトリエ ～アーランドの錬金術士１・２・３～ DX (9121)

Issue transferred from https://github.com/ValveSoftware/Proton/issues/3163.
@BillFleming posted on 2019-10-23T13:11:12:

Compatibility Report

• Name of the game with compatibility issues: Atelier Arland series Deluxe Pack - アトリエ ～アーランドの錬金術士１・２・３～ DX
• Steam AppID of the game: 9121

System Information

• GPU: Vega 64
• Driver/LLVM version: Mesa 19.3/9.0.0 (ACO git AUR 19.3.0_devel.20191017.fe930ad92ab-7)
• Kernel version: 5.3.1
• Proton version: 4.18.r2.ge380c1e9 (proton-tkg staging build from this morning)

Description

After seeing a hint posted from Philip Rebohle I went back and retested all 3 of these games and got them working. This so far only works on the newer staging builds, not vanilla proton yet and not the 4.18 plain wine based custom build.
I set the steam input setting to "Forced Off" as at least in one of the 3 games the x360 controller didn't work with default settings.
I set the following the launch options: "PROTON_USE_WINED3D=1 %command%"

All 3 games I see the menu appear, I can load up my save game, audio works and the game appears to be fully playable now. I will have to wait to provide more info after work but wanted to let yall know.
I see there is already a report just for Rorona, but if it is allowed to have one report for the bundle pack I have posted this separately to cover all 3 Arland games. Note the video does not play still, but you can of course load up the beginning/ending videos in a video player to see them.

using newer version of proton (e.g. 6.3) the game crashes after going a few frames into the main menu. I already tried with ESYNC and FSYNC disabled.
steam-936160.log

The opening video is still being skipped (no test pattern, either), and also the game crashes a second into reaching the title screen

Using Proton experimental-6.3-20211109

https://gist.github.com/ryester27/651917c5bab9ba75198617daf1fa6d0e

On Steam Deck game is working fine at the moment. Opening (intro) video works, gamepad input works, audio works.

Only the launcher needs touchscreen input as mouse cursor does not appear before touching screen. In-game menu works with gamepad though.