openSUSE 15.0, brand new install, fully updated
Running in Virtualbox, but not likely a relevant issue.
Using Firefox 65.5.0esr although IMO that's not likely a relevant issue.

Am reasonably certain it's a problem with with YaST One-Click install on the
client and not OBS.

Errors displayed by YaST
Failed install due to permission problems, then a reference to the YaST logs,
but the error logfile does not exist.

First observed accessing a private repo about 2 mths ago, but dismissed as
possibly a problem with that private repo. But now, am observing this problem
accessing the OSS repo from a brand new, updated LEAP 15.0.

The problem is easily reproducible.
Tested twice for the packages "featherpad" and "git"
- Find the package at https://software.opensuse.org/search
The first noticeable error is that the website does not detect this brand new
LEAP 15 correctly, offers Tumbleweed packages.
- Open the page for the package, find the LEAP 15.0 packages, click to install
using one-click install the default packages (OSS for git, X11:LXQt for
featherpad)
- Proceed as usual to the end, where you will see the install failure and
suggestion to inspect the YaST log, but the logfile will not exist.

It' possible to use zypper to install the package if you don't use the .ymp
file and install the repo (if necessary) and then install using zypper.
One of many ways to locate the information follows, example Featherpad
- From the software search page, click on the "Xll:LXQt" to open the OBS
project page
- Click on "Download package" link
- Click on openSUSE icon
- Scroll down the page "Install repositor and Install Manually"  link.
- Use the zypper command for LEAP 15.0 to install the X11:LXQt repo.
- Refresh repositories and use zypper to install featherpad.

The problem is most likely in the YaST one click install client, probably not
using root permissions even after asking for those permissions.

Am rating this as a Major bug because so many openSUSE Users rely on this
functionality to work and will not know how to find the "install Manually"
procedure.