RDesktop: How to bind Linux client's layout switch to Windows server's layout switch?

Question

linux

I have a Windows Server 2008 that I connect to via RDesktop from a Linux machine.
I have no rights to install any software on the server. I can change the keyboard shortcut for switching layouts: either LeftAlt-Shift, or Ctrl-Shift, or tilde (~).
On Linux, I switch the layout with the right Ctrl - I'm so used to it, and I don't want to relearn. The task is for the RDP client to send the correct combination to the server by pressing the right Ctrl key to change the layout there. That is, so that the layout is simultaneously switched both on the client and in a remote session on the server.
So far, I have solved the problem like this: I created my own configuration file for rdesktop in the home directory. I got this file from the standard file /usr/share/rdesktop/keymaps/ru by cutting out all Cyrillic letters and adding ISO_Next_Group 0x29 to the end of the line. Thanks to this last line, when you press the right Ctrl, a tilde (~) is transmitted to the server. Accordingly, on the server, I switched the switch setting to "tilde". And everything seems to be working, but now I can't type the letter "e". I would like to type it in the standard way - by clicking on the "tilde". But I can't transfer the combination Ctrl+Shift or LeftAlt+Shift (to "untie" the tilde) by pressing the right Ctrl. Can someone suggest a solution?