This explains it. Alt+← is the "Editor: Go Back" keyboard shortcut on Windows (I didn't check what it is on macOS), but that command has a different keyboard shortcut on Linux. The Linux shortcut is Ctrl+Alt+-. Please give that a try.
Something else you might find useful is selecting Peek > Peek Definition from the menu instead of "Go To Definition". This will show the definition/declaration of the object in a inline "peek" view in the editor instead of changing your position in the editor: