Comment 4 for bug 1879168

Thank you for your prompt reply.

I had in fact set `QT_PLUGIN_PATH` btw.

Regardless, I now have a working qpdfview 0.4.14-1, the latest version supported by HP's latest (2020) ThinPro 7.1 OS still based on Ubuntu 16.04 LTS.

### Resolution
The solution was to soft-link qpdfview's libraries to the same directory as the qpdfview binary:

```shell
# cd /media/GenericFlash_sdb1/usr/bin

# ls -l qpdfview
-rwxr-xr-x 1 root bin 1000128 May 17 2015 qpdfview

# ls -l ../lib/qpdfview
total 328
-rw-r--r-- 1 root bin 76848 May 17 2015 libqpdfview_djvu.so
-rw-r--r-- 1 root bin 192784 May 17 2015 libqpdfview_pdf.so
-rw-r--r-- 1 root bin 60136 May 17 2015 libqpdfview_ps.so

# ln -s ../lib/qpdfview/libqpdfview_djvu.so libqpdfview_djvu.so
# ln -s ../lib/qpdfview/libqpdfview_pdf.so libqpdfview_pdf.so
# ln -s ../lib/qpdfview/libqpdfview_ps.so libqpdfview_ps.so
```

### Epilogue
Qpdfview was not the only PDF viewer that did not survive moving to USB stick. HP bundles the lightweight Zathura but is no minimalistic as to be only useful in-browser. Research was made of standalone PDF readers on https://alternativeto.net/?platform=linux applicable to the latest supported version of HP's Thin Client operating system.

#### Results
1. Atril (MATE Document Viewer 1.12.2) complains that it can't find backends. Not yet reported to developer so not currently known whether a fix or workaround will be made available.

2. Evince (GNOME Document). Will not run from non-installation directory and developers will not fix or provide a work-around (https://gitlab.gnome.org/GNOME/evince/-/issues/1412).

3. Foxit Reader 2.4.4.0911 (2017) Free version of commercial product. Modern, high-quality, interface runs straightforwardly.

4. MuPDF 0.9 (2011) Minimalistic. Runs straightforwardly.

5. PDF Studio Viewer 2019.2.2 (2019) Free version of commercial product. Runs straightforwardly (Java-based). Modern, high-quality (so impressed, have bought top-end 'Pro' product).

6. Qpdfview 0.4.14, Modern tabbed viewer with annotation capabilities. Will run if its supplied libraries are linked to execution directory.