How to install .NET framework v4.0.30319 on wine?
Solution 1:
With winetricks and a 32-bit WINE prefix. Be in mind, that PlayOnLinux use a separate wine prefix for each installed applications. For this reason, you have to use your WINEPREFIX:
sudo apt-get install winetricks
WINEARCH=win32 WINEPREFIX=~/.wine32 winetricks dotnet40
But as you can read here, the installation script for osu
Script is outdated and no longer works.
And couriosly, osu needs dotnet20 and not dotnet40.
Solution 2:
Try following the Official Documentation on installing Osu! on the winetricks hq