How Mac keyboard can issue Alt key input in Apache Guacamole

Question

I am using XFCE terminal in Debian linux on Apache Guacamole from MacOS X.

I'm trying to navigate between tabs in the XFCE's terminal using ALT key shortcuts (e.g. ALT+1 and ALT+2) like shown in the screen below:

I've tried every key combination I can think of, plus researched at places like this. But I haven't yet figured out the secret.

How can I issue these ALT- key combinations from my Mac keyboard in Guacamole?

Answer 1

Usually the modifier key ALT on a PC means "alternate" which would translate to Mac's keyboard symbology as Option (on some Macs drawn with a branching-switch icon):

Solution (when Guacamole uses realVNC)

According to realVNC (one of the possible connection protocols by Guacamole) your needed "from Mac to PC" key mapping would be:

• Pressing "CmdL" (left Command key on your local Mac) will result in "AltL" (left Alt key on the remote PC/Linux)

Insightful thoughts

When using Guacamole, which probably uses VNC or XRDP protocol to connect your local client (Mac) to the remote server (Linux), the keyboard mapping has to pass 2 layers, from your local hardware/OS (Mac) to browser, over Guacamole/XRDP to the remote-system (Debian with XFCE). All these layers can interpret the key-events triggered.

Research

Like a user of this XRDP-related forum post from MacRumors (from 2015) explains:

As below link states, Alt key of PC keyboard should be mapped as Option key on OS X. This is what we see on ARD. On XRDP Alt key behaves like Windows key and is mapped to Command key.

See also:

• RealVNC Help Center: Keyboard Mapping To and From a Mac
• AskDifferent: Can't get Alt (Option) key to work while remote controlling a Mac from Windows with VNC, reverse direction, but might give a clue
• AskUbuntu: Remote desktop to Ubuntu has wrong keyboard mapping
• Griffon's IT Library blog: XRDP – How To Make your keyboard “special keys” (Alt+Gr, Up,Down,..) working when using XRDP