

Second controller stopped working once entering the chapter select board. GE9-20 fixed this for me.
Chapter select would disable second controller: luckily GE9-20 fixed this compared to standard proton.

Great OOTB
Had some issues where one of the players couldn't move but I think it was due to pressing the key combo that changes WSAD to the arrow keys (?)

This game requires some specific DLL files, so I highly recommend using ProtonGE to avoid graphical bugs.
When first launched, the game will run at the lowest resolution, we have to adjust it manually in the options menu.
My suggestion, use the latest version of ProtonGE.
performance drop on non-gaming machine

Just a lot of fun. Played mostly couch co-op.
Game runs even perfectly at 1080p

Works great

Works great even with the high gpu usage
GPU usage is very high for the game but it still plays at a steady 60 fps

minor gaphical artifacts in bathroom sections

Game crashes after an hour without Proton-GE. With it I played through the entire game with no issues.
I had to switch to an older version of Proton and add some launch options in order to play this game. After that, it worked perfectly.
PROTON_NO_ESYNC=1 unset LC_ALL && %command%

PROTON_NO_D3D11=1 unset LC_ALL && %command%
to fix massive performance issues, navigate to .steam in your home folder and search for pcconfig.txt, you WILL NOT find this in the steamapps/common folder, open the pcconfig.txt file and set the value of ForceMultithreadedD3D to 1 also enable vsync(not nessesairy) u can use this for every lego game, it will improve performance massively
set ForceMultithreadedD3D to 1 in pcconfig.txt to fix this issue

Without GE-Proton the game would crash after an hour of play.
Controllers would randomly disconnect and the game would refuse to let them back in.

game crashes in random moments, it's hard to enjoy it because of that

Game works perfectly out of the box, no issues at all.
In-game config: Enabled FSAA, Changed display resolution to 1280x800
Crashes about once an hour while playing
Works out of the box, reached a 100.0% save from scratch.
You can play the first 2 years entirely, but from the last level of the third year there is a bug in the gargoyle puzzle that crashes the game, it's a problem with the PC version that affects here as well. You cant complete the entire game
If you live outside of the US, chances are that you are unable to save the game. Here's why.
There's an annoying bug in Steam OS. People outside of the US set their system's settings to a foreign locale, in my case German. This causes date formats and also system paths to change slightly.
There's a bug in Steam OS though that can't 100% change the locale. And when using the Konsole app in Desktop Mode, it's clear. You will constantly get errors complaining about locale or LC etc.
This error messes with LEGO Harry Potter. My guess is that Steam OS tries to translate some in-game folder paths and fails to do so.
Fortunately the solution is simple. I've posted the guide here: https://steamcommunity.com/app/1675200/discussions/0/5135803832902211410/
In short, disable file system's read only mode, reinstall glibc, generate the locale.
In long:
- Run Desktop Mode
- Open Konsole and run (without ">"):
sudo steamos-readonly disable sudo pacman -Syu glibc sudo locale-gen
See my fix.
If you live in the US or you set your system's locale to US, everything should work fine out of the box. If not, use my simple fix: https://steamcommunity.com/app/1675200/discussions/0/5135803832902211410/#c3466100515584689608
sudo steamos-readonly disable sudo pacman -Syu glibc sudo locale-gen
Only saves and starts new game in Desktop Mode on Deck
Game Mode doesn't appear to create or detect relevant save and config files - "Failed to Save"
Using Proton 7.0.4 and have tried various GE and standard versions.
The game has some glitches (that are there on Windows too). Using a Time Turner, sometimes the screen blacks out fix. In the level where you rescue Sirius from the tower, it freezes fix.
Both fixes involve editing the pcconfig.txt file, found at ~/.steam/steam/steamapps/compatdata/21130/pfx/drive_c/users/steamuser/AppData/Roaming/WB Games/LEGO® Harry Potter™/pcconfig.txt
. Setting all values from InvertY
down to the bottom to 0
fixes the glitches, though it also impacts the lighting.
Lighting glitches which are also present natively on Windows.

You need to make sure that the install the "Steamworks Common Redistributables" package is installed or the needed DirectX and Visual C runtimes will not install, causing the game to blink like crazy, not load the shaders properly, and eventually crash.
No tweaks are needed as long as the "Steamworks Common Redistributables" package is installed, otherwise the game will malfunction and crash.
(>^-^)> Worked flawlessly out of the box! <(^-^<)
There is a minor artifact (I think it appears after sleep) in which some spells generate a thin circle of digital garbage. Looks pretty cool tbh, but annoying. Also, when switching from external display to internal, you get two things: more and heavier arifacts like previously mentioned and also tha game is confused about aspect ratio and stretches or pushes the images after the change, even though the resolution is perfectly set. Definitely don't take the game from one screen to the other. Close it, change screens, open it again and check the settings to be the correct ones.
Had a problem that if the second player is KB/M you can't remove them if they disconnect. Also, you can't really do some settings if such a player joins. If they leave nicely or close the game with them on, there shouldn't be any issue.
Battery life is amazing and the game looks decently good on the Deck's small screen.
There are some minor artifacting problems in the underwater levels in year 4. but worked great from start to finish.
Without switching to 6.3, it wouldn't launch. Once switched it worked fine out of the box, I just had to adjust the screen resolution.
Save data is deleted when the game is uninstalled. No Steam Cloud support.
Have the same problem with this game as with the sequel, It won't start.
Using, Proton 7.0-3. Also tried Proton Experimental and verified integrity of game files.
Game loads but graphics do not render
All geometry in the game is rendered with seizure-inducing colors; tried with both 6.3-18 and EXPERIMENTAL.

Only tested with Proton 6.3, though I doubt newer versions would introduce any problems.
Runs perfectly out-of-the-box
Sometimes light sources have slightli transparent checkerboard over it. It's very minor and does not interfere with the game
The game crashed twice during all chapters
Some blocks have broken physics and fly to the sky, so you have to time grabbing it to be able to complete the level
Minor problems but overall good experience
Slight artifacting when casting certain spells
Fixes in beta branch of steam OS will likely soon be brought down to stable

Graphic Bug - Flashing squares of multiple colors
Unplayable, tried every version of proton as well as the Flatpak vs native installation. Doesn't seem to play well with my 3080ti it seems. Going to have to run this one in my VM
Works perfectly fine.
Works fine on T430
It did work with flatpak version of Steam. When I tried native package, game had some texture bugs / flashing lights so it was unplayable.