When installed using flatpak or tarball in Ubuntu 20.04 no preferences option shows in the menu

[beetlejuice16]

First issue submission. Hope it's up to standard.

I installed marker on my laptop running fedora and loved it, especially because there were a ton of themes for the editor and previewer in the preferences menu.

I installed it on my PC running Ubuntu 20.04 and the options are non-existent when clicking on the hamburger menu in the top right. I tried looking through previous issues to see if it has been discussed before but I couldn't find anything. I have attached a screenshot to show what I mean.