OK then. I rebooted and UI apps now appear to work again. What's with that? I had rebooted the machine a few times previously - without joy. UI apps remained indubitably broken. Now, for *some* reason, all is well in the UI world again. However, I do notice that running `env` at the shell prompt now displays *waaaaay* more definitions than previously when nothing UI-ish was working - including variables called DISPLAY, WAYLAND_DISPLAY etc., etc. 
A timing issue? Or a rehash issue?

Having the same issue.  It was working on this version before a reboot.  Now no amount of rebooting seems to be fixing it due to the missing env variables.

This is fixed with the 11101.0.0 component push. You may need to manually kick an apt upgrade:

crosh> vsh termina
(termina) chronos@localhost ~ $ lxc exec penguin -- apt upgrade
(termina) chronos@localhost ~ $ lxc exec penguin -- poweroff

and then relaunch the Terminal app.

Also make sure the cros-termina component version is 11101.0.0 under chrome://components, and restart the VM. This will allow the cros-apt-config upgrade to complete.

Thanks. 

My UI's actually started working before the fix. I'd run `apt upgrade` a few times, and various attempts with apt-get and dpkg. I constantly received an error while trying to upgrade 'cros-apt-config' (there's a bug report filed by someone else about this from a few days ago).

After refreshing chrome://components, rebooting and issuing the lxc commands the upgrade went through without error.

As an FYI, the error I'd been receiving earlier was 

Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages will be upgraded:
  cros-apt-config
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/7364 B of archives.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
(Reading database ... 57458 files and directories currently installed.)
Preparing to unpack .../cros-apt-config_0.14_all.deb ...
Unpacking cros-apt-config (0.14) over (0.12) ...
dpkg: error processing archive /var/cache/apt/archives/cros-apt-config_0.14_all.deb (--unpack):
 unable to make backup link of './etc/apt/sources.list.d/cros.list' before installing new version: Invalid cross-device link
Errors were encountered while processing:
 /var/cache/apt/archives/cros-apt-config_0.14_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
(termina) chronos@localhost ~ $
 

Verified on 11137.0.0, 71.0.3567.0 on eve.