Hello @naparts and welcome to the forum 
Which Linux distribution are you using and which version of krita?
Where did you get krita form and how is it installed?
(e.g. distro repo, snap, flatpack, appimage.)
Have you used krita for a long time and has this problem always existed?
If the problem hasn’t always existed, what is the history of the problem development?
(e.g. Did it happen as soon as you upgraded the krita version number or after you upgraded your Linux distribution?)
A similar problem was reported by @kazarts in a topic reply here:
Krita will not rearrange Keyframes in the timeline or Storyboard docker - #6 by kazarts
Please read that topic and see if it is also applicable to you and if the suggested attempt at a solution works for you, here:
Krita will not rearrange Keyframes in the timeline or Storyboard docker - #12 by AhabGreybeard
If you don’t know animating in krita then don’t worry about trying the animation actions.