'Alt' keyboard shortcuts seem to not to be forwarded to the server correctly

[stdedos]

Ctrl+Shift+D, Ctrl+C works.
Ctrl+Alt+Y, Ctrl+Shift+Alt+C don't work:

"Xpra-Python3_4.0.2-r26623\xpra_cmd" attach ssh://user@ip/2 --ssh="plink -ssh -agent" --modal-windows=no --title="@title@ on @@/@server-display@" --opengl=no --bandwidth-limit=6Mbps

2020-07-08 10:21:21,525 Xpra GTK3 client version 4.0.2-r26623 32-bit
2020-07-08 10:21:21,527  running on Microsoft Windows 10
2020-07-08 10:21:22,419 GStreamer version 1.16.2 for Python 3.8.3 32-bit
2020-07-08 10:21:22,925 keyboard layout code 0x409
2020-07-08 10:21:22,925 identified as 'United States - English' : us
2020-07-08 10:21:23,257  keyboard settings: layout=us
2020-07-08 10:21:23,260  desktop size is 4160x1440 with 1 screen:
2020-07-08 10:21:23,261   Default (1100x380 mm - DPI: 96x96) workarea: 4160x1400
2020-07-08 10:21:23,261     Generic PnP Monitor 1600x900 at 0x534 (309x174 mm - DPI: 131x131) workarea: 1600x860
2020-07-08 10:21:23,261     C32JG5x 2560x1440 at 1600x0 (697x392 mm - DPI: 93x93) workarea: 2560x1400
2020-07-08 10:21:28,266 enabled remote logging
2020-07-08 10:21:28,268 Xpra GTK3 X11 server version 3.0.10-r26630 64-bit
2020-07-08 10:21:28,268  running on Linux Ubuntu 16.04 xenial
2020-07-08 10:21:28,273 Attached to ip:22
2020-07-08 10:21:28,274  (press Control-C to detach)

Attaching small server logs.

xkbprint -label name $DISPLAY: empty
Missing #2830

[Antoine Martin]

Unless I am missing something, the remote keyboard state looks correct and has Control_L + Shift_L + Alt_L + C.
What application can I use for testing this specific shortcut?

[stdedos]

PyCharm: Reload all from disk / Copy Reference at cursor.

For the latter:
Open any random project and file, move somewhere, and press it.
It should copy: path-from-project-root(:lineno|#method)

[stdedos]

Oops: Missed Server/Client

[stdedos]

Okay, I found the problem:

I don't understand the "how" or "why", but xpra+PyCharm does not like this.
Normal X11+PyCharm works OK.

gnome-terminal does not complain either (e.g. Alt+BkpSpace)

"Xpra-Python3-x86_64_4.1-r26973\xpra_cmd" attach ssh://user@ip/2 --ssh="plink -ssh -agent" --modal-windows=no --title="@title@ on @@/@server-display@" --headerbar=off --opengl=no --bandwidth-limit=6Mbps

2020-07-20 12:25:05,095 Xpra GTK3 client version 4.1-r26973 64-bit
2020-07-20 12:25:05,097  running on Microsoft Windows 10
2020-07-20 12:25:06,071 GStreamer version 1.16.2 for Python 3.8.3 64-bit
2020-07-20 12:25:06,680 keyboard layout code 0x409
2020-07-20 12:25:06,680 identified as 'United States - English' : us
2020-07-20 12:25:06,908  keyboard settings: layout=us
2020-07-20 12:25:06,913  desktop size is 4160x1440 with 1 screen:
2020-07-20 12:25:06,916   Default (1100x381 mm - DPI: 96x96) workarea: 4160x1400
2020-07-20 12:25:06,916     Generic PnP Monitor 1600x900 at 0x534 (309x174 mm - DPI: 131x131) workarea: 1600x860 at 0x534
2020-07-20 12:25:06,916     C32JG5x 2560x1440 at 1600x0 (697x392 mm - DPI: 93x93) workarea: 2560x1400 at 1600x0
2020-07-20 12:25:10,903 enabled remote logging
2020-07-20 12:25:10,907 Xpra GTK3 X11 server version 3.0.10-r26630 64-bit
2020-07-20 12:25:10,909  running on Linux Ubuntu 16.04 xenial