Ubuntu 20.04 + tmux: shift (or Alt) + arrows doesn't move, just output key code in console

Description of the problem or steps to reproduce

When running micro in tmux, the Shift-arrow and Alt-arrow output a key code in the console:

Shift Left : [1;2C]
Shift Right: [1;2F]
Shift Up   : [1;2A]
Shift Down : [1;2B]
C-Sht Right: [1;6C]
C-Sht Left : [1;6D]
C-Sht Up   : [1;6A]
C-Sht Down : [1;6B]

Alt Up/Dn  : [1;3A] [1;3D]
Alt Left   : [1;3D]
Alt Right  : [1;2C]
Alt { or } : nothing happens

• Editing the file using nano (still within tmux) the modifierKey-arrow works OK.

• Running micro OUTSIDE of tmux the problem disappear, ie. the modifierKey-arrow does perform their intended action.

This seems to be an issue of micro + tmux. But I don't have any keybindings in tmux for those keys combination. Would appreciate if you can help to for a solution.

Thanks

Specifications

micro -version
Version: 2.0.10
Commit hash: b976385
Compiled on August 07, 2021

OS: Ubuntu 20.04.3.
Terminal: tmux 3.0a

My .tmux.conf doesn't have anything special. The issue described above exists whether the below tmux settings are set or not.

set-window-option -g xterm-keys on
unbind S-Left
unbind S-Right

Reproduce the modifier-arrow behavior with micro 2.0.10 inside tmux 3.0a on Ubuntu 20.04. Compare it with micro outside tmux and with nano inside tmux, then check whether the relevant tmux.conf settings affect the result; done means Shift- and Alt-arrow combinations perform their intended editor actions instead of printing key codes.