
Good
Goofy lag when in online, but it's short lived
Has some goofy physics, but I'm pretty sure it's part of the game design, not Proton.

Played multiple matches and had no issues.

No audio
No audio was present

Kinda slow but playable
Significantly lower fps than on Windows
lags
gamemoderun %command%
PROTON_USE_WINED3D=1 %command%
Pressing esc to quickly makes all walls and minor objects disappear
Input was delayed or ignored, could be system hardware
On load screen game sometimes crashes
Was able to play online multiplayer first try without any changes.
Proton 6.14-GE-2 is my default Steam proton version, and this game worked out of the box with no further adjustments.
Multiplayer doesn't work in the 2020 version.
Can't do nothing about online.
Only 2015 version could connect to Online servers, but it lacks content and has significant amount of bugs.
It was not loading because I had 0B free on disk

This game has its faults, but the experience is definitely enjoyable for some quick matches with friends.
6.21-GE-2 GloriousEggroll
Proton 6.21-GE-2
Depth of Field blur not working as intended and with Mirrors showing inverted environments.
in the Classic 2015 version of this game there are significant performance issues, with the 2020 version however, there are still performance issues but on a much lesser degree.
In the 2020 version specifically, when beating a game whether its offline or online, the game will stop responding.
Despite the performance degradation this game has, I could see people having a good time playing this game. I would Recommend the 2020 version however, as the 2015 version of this game in my experience runs worse, which may be able to be partially solved with tinkering of settings, but I would recommend the 2020 version.

Despite it's performance issues, the Playtest (2020) version works decently for an occasional match.
The Depth of Field effect in the Classic (2015) version was broken and applied blur improperly, and reflections were mirrored.
Video Playback on the TV party screen in the Playtest (2020) version does not work out of the box and requires either Proton GE or the Media Foundation DLL to resolve.
The Classic (2015) version had significant performance issues whilst the Playtest (2020) version had noteworthy but not as significant performance issues.
In the Playtest (2020) version, every time a match ends the game locks up on a black screen. This issue isn't present in the Classic (2015) version.
As it stands at this current time, Who's Your Daddy does technically run on Linux out of the box, but both the 2020 and 2015 versions greatly underperform. With something like Proton GE, you can have the 2020 version render practically on par to what it does on Windows, but with freezing at the end of each match, it's not an ideal experience. For a quick game or two, it might be annoying, but if you can put up with it, it'll work.
Very low FPS
Both version run perfectly OOTB (Proton 5.0-10). No noticeable degradation from running through Proton

Unmöglicher Spielstart.
Das Spiel lässt sich auf keiner Version von Proton starten. Vielleicht könnte man, wenn man etwas bastelt, ein work around finden. Aber als SteamPlay Erlebniss ist es ungenügend.
It opens but doesn't run
Default installation shows only garbage on the screen -unusable!
This happens if I change the launching parameters of the game:
Steam Linux Runtime = garbage on screen
PROTON 4.11-11 = game runs fine