There is a new drum king coming to Linux!!!
Speedrum 2 is currently in beta, and I don't know of a better app on Linux for drums! I currently own version 1, and the upgrade path is really fair. In addition, there is currently a discount for those who buy while it is in beta. Check it out!
https://www.apisonic-audio.com/speedrum2.html
I'm REALLY excited about this news!! I've been wanting a drum sampler that could handle more layers! 
