I installed Ubuntu 18.04.2 64 bit LTS GNU/Linux with Linux kernel version 5.0.6 64 bit and I am using a new XFX AMD Radeon VII GPU. I researched the Phoronix article to download the firmware files and I put them into /lib/firmware/amdgpu and I bought Tony George's Ubuntu Kernel Update Utility and licensed it to install the latest Linux kernel version. After I restarted, my AMD GPU was properly detected and it just works. I installed JRiver Media Center 24 and 25, but not at the same time and licensed both of them separately. I successfully imported my private media library, but under the Videos section, very few preview thumbnails showed up in either version. Most of my defined categories under the Video section show up empty with almost no preview thumbnails. I did use VLC to play my videos, movies and TV shows and each title plays just fine.
I also own a mid-2017 ASUS ROG STRIX GL702ZC gaming notebook PC and a mid-2018 Huawei Matebook X Pro Intel Ultrabook laptop and I recently installed Ubuntu 18.04.2 64 bit LTS GNU/Linux on each laptop along with JRiver Media Center 25 Master License 64 bit. I am using JRiver Media Center version 25.0.15 64 bit right now on my three Ubuntu powered PCs. For both laptops, my Videos section appears normal and I can see preview thumbnails for the same titles and play them within the software product. This is not the case for my mid-2017 AVA Direct gaming desktop PC and I do not know why.
How can I get useful technical information to this community to investigate why this technical issue exists and how to solve it?