VCP launches in gladevcp, but errors from linuxcnc

(gladevcp:213239): Gtk-WARNING **: 19:09:22.058: GtkPlug only works under X11
<commandline>:0: gladevcp exited without becoming ready

$ linuxcnc axis.ini 
LINUXCNC - 2.10.0~pre0
Machine configuration directory is '/home/rmann/camsync-vcp'
Machine configuration file is 'axis.ini'
Starting LinuxCNC...
emc/iotask/ioControl.cc 786: can't load tool table.
linuxcnc TPMOD=tpmod HOMEMOD=homemod EMCMOT=motmod
Note: Using POSIX non-realtime
Found file(lib): /home/rmann/linuxcnc/lib/hallib/core_sim.hal
Found file(lib): /home/rmann/linuxcnc/lib/hallib/sim_spindle_encoder.hal
Found file(lib): /home/rmann/linuxcnc/lib/hallib/axis_manualtoolchange.hal
Found file(lib): /home/rmann/linuxcnc/lib/hallib/simulated_home.hal
Found file(lib): /home/rmann/linuxcnc/lib/hallib/check_xyz_constraints.hal
note: MAXV     max: 5.000 units/sec 300.000 units/min
note: LJOG     max: 5.000 units/sec 300.000 units/min
note: LJOG default: 0.250 units/sec 15.000 units/min
note: jog_order='XYZ'
note: jog_invert=set()
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
[GladeVCP][INFO]  Logging to: /home/rmann/gladevcp.log (logger.py:107)
[GladeVCP.QTVCP.QT_ISTAT][WARNING]  Embeded tab configuration -invalid number of TAB_NAMES vs TAB_LOCATION - guessing default. (qt_istat.py:421)
Version:  3.11.1 (main, Dec 31 2022, 10:23:59) [GCC 12.2.0]

(gladevcp:213239): Gtk-WARNING **: 19:09:22.058: GtkPlug only works under X11
<commandline>:0: gladevcp exited without becoming ready
Embeded tab command "halcmd loadusr -Wn camsync gladevcp -c camsync -u ./camsyncvcp.py -x 12583336 ./camsync.ui" exited with error: 1
Shutting down and cleaning up LinuxCNC...
task: 1017 cycles, min=0.000002, max=0.007927, avg=0.001155, 0 latency excursions (> 10x expected cycle time of 0.001000s)
Note: Using POSIX non-realtime
LinuxCNC terminated with an error.  You can find more information in the log:
    /home/rmann/linuxcnc_debug.txt
and
    /home/rmann/linuxcnc_print.txt
as well as in the output of the shell command 'dmesg' and in the terminal

$ gladevcp -c camsync -H camsync.hal -u camsyncvcp.py camsync.ui 
[GladeVCP][INFO]  Logging to: /home/rmann/gladevcp.log (logger.py:107)
tool_mmap_user(): tool mmap not available
poll(): continuing without tool mmap data
Version:  3.11.1 (main, Dec 31 2022, 10:23:59) [GCC 12.2.0]