Yes, you can continue to use Holdem Manager 2 while playing. Despite the end of its support period, most poker sites trackers will still display HUD and import hand histories. Now, however, any major update to the PokerStars poker client (substitute the name of your favorite room) could be fatal.
Supported Sites & Languages\n\n HM3 supports more than 12 major poker networks including: Poker Stars, Party Poker, Microgaming, Ipoker, Merge Network, Pacific/888, Boss Network, Winning Poker Network, Peoples Poker, Winamax, Bovada/Ignition/Bodog, PPPoker and Poker Kingdom.