Have a few minutes to kill here and there? Sandtrix could be what you need. It's free, has a Linux version and got the attention of Tetris Holding, LLC under the previous name Setris so it got a DMCA takedown but now it's back. But for how long?
The original page on itch.io for Setris is gone and just has a link to the copyright complaint from Tetris Holdings, because the Setris name was so similar (and it noted the use of a "Russian Folk Song Registered Trademark") on top of that. So the developer has renamed it to Sandtrix and put it back up. I wasn't even aware of it until now thanks to the DMCA so it's actually given it a bit of a boost.
Quite a fun spin on the basic idea of falling blocks. They come down in the usual shapes, but when they hit the bottom or some sand already there, they crumble into pieces. You need to cover an entire row from left to right in one colour to have it vanish and up your score. Really sweet to kill a few minutes.
Head to the itch.io page to check it out.
Looking around it probably got the attention of Tetris Holding because Kotaku and RPS both covered it recently when it was called Setris. So they must have people constantly looking around for anything resembling Tetris to strike.