Linux Viewer do not respect right side modifier buttons
This is a bug report. If using Linux Viewer (14.1.18533 on ArchLinux), you cannot send CTRL_R, SHIFT_R and ALT_R modifiers, as well num pad presses are sent as mainpad buttons. I was trying to use VirtualBox on a remote machine, and I could not escape from it, because it uses right control button for it. Windows Viewer do not have such issue (it can send right alt, ctrl and shift normally) and it is nothing to do with "send key combinations" checkbox.
Also I wanted to mention, that I have not found utility like xev for Windows. However, I have found the only one online keyboard checker that correctly can determine left or right modifier: it is https://keycode.info/ So you can use it to check on Windows clients.
Re: Linux Viewer do not respect right side modifier buttons
Also bacause this is related to key handling in linux and is a minor issue, I want to share it here: When you connect from Linux Viewer to Windows Client and Num lock is active in Windows, then when you are sending key presses, teamviewer makes "numlock release", then sends a key, and then again "activates numlock". I think it should also be fixed.