Thanks for reporting.
The real problem looks to be this:
install of bluedevil-5.27.12-1.x86_64 conflicts with file from package plasma6-bluedevil-6.3.4-2.x86_64
Does not install from OM-Welcome. I got a different but similar error:
install of okular-common-23.08.5-2.x86_64 conflicts with file from package plasma6-okular-common-25.04.0-1.x86_64
Both errors are the script wanting to install old Plasma5 package which conflict with installed. Plasma6 package.
Possibly something in the script used by OM-Welcome needs to be changed?
I can confirm that the package installs from cli.
This appears to be a problem related to OM keeping Plasma5 while also using Plasma6. Since Plasma5 is finally being removed in Cooker this stuff will get fixed eventually but it may take some time. A lot of this should be fixed by the next big upgrade for ROME which will remove the Plasma5 stuff. I am hoping for that to happen very soon. 