You can look up 2 opinions in this thread: https://www.speedrun.com/streaming_recording_equipment/thread/ccj1i

The only fully featured one I've found is Llanfair (Gereds fork). People hate it because it's less featureful than Livesplit, but it has global hotkeys. It's Java so it'll work for a while to come. https://github.com/gered/Llanfair/releases/tag/1.5.4

Other options include:

Flitter: https://github.com/alexozer/flitter (Terminal timer, quite nice, but hard to change settings) Urn: https://github.com/3snowp7im/urn (Aims to mimic Livesplit, again has settings that are hard to change) And any more people care to mention (I'm sure I've seen more, but these are the two I can find in my history)

I just today made a Linux build for my timer, Runtime ( https://dartfling.com/product?pid=7 ). It's pretty simple, but it has global hotkeys and a basic split manager, and even displays what keys are being pressed. Hope you enjoy!