For a long time I always found the linux icon out of alignment, I attribute this problem that was perhaps related to my system fonts. But I think that need a HACK for Linux / Ubuntu

Tests:
Os: Kubuntu / KDE
JDK: OpenJDK 7 and 11

But I decided to investigate further, and looking at some prints on the internet I see that it is really out of alignment.

http://dexvils.blogspot.com/2015/06/install-arduino-ide-16x-on-ubuntu.html
https://websiteforstudents.com/how-to-install-arduino-ide-on-ubuntu-18-04-16-04/