Você pode instalar o wireshark-gtk e usá-lo em vez de wireshark:
ubuntu@mrouter02:~$ sudo apt install wireshark-gtk
...
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Setting up wireshark-gtk (2.2.6+g32dac6a-2ubuntu0.16.04)
...
ubuntu@mrouter02:~$ wireshark /tmp/dbus.pcap
failed to get the current screen resources
The X11 connection broke: I/O error (code 1)
XIO: fatal IO error 2 (No such file or directory) on X server "localhost:11.0"
after 349 requests (349 known processed) with 0 events remaining.
ubuntu@mrouter02:~$ wireshark-gtk /tmp/dbus.pcap
** (wireshark-gtk:8621): WARNING **: Couldn't register with accessibility
bus: Did not receive a reply. Possible causes include: the remote application did not send a reply,
the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
ubuntu@mrouter02:~$
Os avisos não estão afetando a usabilidade do wireshark-gtk.