In 22.214.171.124 Fresh, the KDE4 Oxygen icon pack is no longer bundled with LO. I'm making the wild assumption that all Linux packages/installers are affected, though this was found to be true for the x86_64 RPMs.
Fortunately I still had my 126.96.36.199 RPMs handy, so I extracted images_oxygen.zip from libobasis5.3-images-188.8.131.52-2.x86_64.rpm, put the file somewhere safe, and then symlinked it from there into /opt/libreoffice5.4/share/config/. All is well again.
Despite my straightforward workaround above, please, please, please tell me that its absence is an oversight and not intentional. It seems to me that between releases, Oxygen was substituted with Sifr Dark.
Steps to Reproduce:
1. Install 184.108.40.206. In the View options try to set Oxygen as the icon style.
No Oxygen icons.
Oxygen icons. (These new mandatory fields are a bit of a pain...)
User Profile Reset:
Icon sets previously bundled with 5.3.4.02:
$ rpm -qlp libobasis5.3-images-220.127.116.11-2.x86_64.rpm
Icon sets currently bundled with 18.104.22.168:
$ rpm -qlp libobasis5.4-images-22.214.171.124-3.x86_64.rpm
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
duplicate of bug 110353.
Best regards. JBF
*** This bug has been marked as a duplicate of bug 110353 ***