Don't know what I did with my last answer.. Here it goes again: I play on pokerstars on linux mint, through wine. Works ok.
I've been trying to install partypoker through wine, but it crashes often. I will try more to make it work.
The most Linux friendly sites I've found are Seals With Clubs and Carbon. ignition used to work on Linux through the Vivaldi browser, but that option no longer exists.