Some addition to **Debian 10** (Gnome, X11) from above:
``` ctrl + [ #(2 729109 27 0 2 91 0 1) ctrl + ] #(2 773893 29 0 2 93 0 1)
ctrl + { #(2 564471 27 0 3 123 0 1) ctrl + } #(2 665358 29 0 3 125 0 1)
ctrl + C #(2 808422 67 0 3 67 0 1) ```
So, it seems that only for ctrl + Aa-Zz those ASCII and Unicode codes got duplicated. That's very strange.