[BUG] - im using r2modman to mod ultrakill on ubuntu mate linux, and its asking me to select the installation folder for it, but its not letting me

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Description of the bug
in settings, when i scroll to "select ultrakill installation folder" and click on it it opens up the file manager, and the window is labled "select ultrakill executable", with the box in the lower right corner thats usually for selecting file types is just ultrakill, not a file type. but when i navigate to the folder, it doesnt show the file, just the other folders.

To Reproduce
Steps to reproduce the behavior:

1. Go to change ultrakill directory (it says to manually set it right below)
2. Click on it
3. navigate to the folder
4. theres just the other folders, the actual executable, or any other files, isnt there

screenshot:

there should be a grey icon with a gear labled "ultrakill" in that screen shot, but there isnt. (I have checked the actual folder, its there, it just doesnt show up when going to select it from r2modman)