Lukako Managed to change most of my MW3 settings through a .cfg file. Having the same issue as @T6Aro where starting BO just results in a DirectX error with no logging. Ditching Lutris and just going with wine works there as well...
Also, are you guys able to connect to friends in custom games? I'm not sure if connection errors are on my end or not, I can connect just fine to any dedicated server.