Christian,
Thank you for the details and the screenshots.
While we try to replicate the problem at our end, can you please also share with us the OS theme and Eclipse theme (i.e the workbench theme selected in the DevStyle > Color Themes preferences page) selected for a particular OS? You can share the details for Ubuntu/Mint along with the exact version of the OS.
Apologies for inconvenience caused.
–Swapna
Genuitec Support