If your client and server computer does not have the same keycode or key combination for the same key, you may need to use a temporary workaround to resolve this issue.
For example, your key code for Server (Linux) is ISO_Level3_Shift while your key code for Client (Windows) is Alt_R.
The workaround is to redirect the key code at the OS level. For example, if you do not use your Right Ctrl key much, you can map it to a new key code such as Alt+R. This way, you can use Ctrl+R if you need to make Alt+R work on your client computer.
To configure this in your Linux Server:
> xmodmap -pke > "$HOME/.Xmodmap"
> nano "$HOME/.Xmodmap and add: keycode 105 = Alt_R Meta_R Alt_R Meta_R
> crontab -e and add this: @reboot sleep 30 && DISPLAY=:0 xmodmap ~/.Xmodmap