Base on instruction of following link to upgrade system 15.3->15.4, conflict
happen.
https://en.opensuse.org/SDB:System_upgrade_to_Leap_15.4

openqa-migration-qe1-1:~ # zypper --releasever=15.4 dup --download-in-advance
Warning: Enforced setting: $releasever=15.4
Loading repository data...
Reading installed packages...
Warning: You are about to do a distribution upgrade with all enabled
repositories. Make sure these repositories are compatible before you continue.
See 'man zypper' for more information about this command.
Computing distribution upgrade...

Problem: nothing provides 'yast2-qt-branding' needed by the to be installed
yast2-theme-4.4.4-lp154.2.2.1.noarch
 Solution 1: deinstallation of yast2-theme-4.3.11-3.6.1.noarch
 Solution 2: keep obsolete yast2-theme-4.3.11-3.6.1.noarch
 Solution 3: break yast2-theme-4.4.4-lp154.2.2.1.noarch by ignoring some of its
dependencies

Choose from above solutions by number or cancel [1/2/3/c/d/?] (c): c
openqa-migration-qe1-1:~ # zypper lr -u
Repository priorities are without effect. All enabled repositories share the
same priority.

#  | Alias                       | Name                                        
                                               | Enabled | GPG Check | Refresh
| URI
---+-----------------------------+---------------------------------------------------------------------------------------------+---------+-----------+---------+------------------------------------------------------------------------
 1 | repo-backports-debug-update | Update repository with updates for openSUSE
Leap debuginfo packages from openSUSE Backports | No      | ----      | ----   
| http://download.opensuse.org/update/leap/15.3/backports_debug/
 2 | repo-backports-update       | Update repository of openSUSE Backports     
                                               | Yes     | (r ) Yes  | Yes    
| http://download.opensuse.org/update/leap/15.3/backports/
 3 | repo-debug                  | Debug Repository                            
                                               | No      | ----      | ----   
| http://download.opensuse.org/debug/distribution/leap/15.3/repo/oss/
 4 | repo-debug-non-oss          | Debug Repository (Non-OSS)                  
                                               | No      | ----      | ----   
| http://download.opensuse.org/debug/distribution/leap/15.3/repo/non-oss/
 5 | repo-debug-update           | Update Repository (Debug)                   
                                               | No      | ----      | ----   
| http://download.opensuse.org/debug/update/leap/15.3/oss/
 6 | repo-debug-update-non-oss   | Update Repository (Debug, Non-OSS)          
                                               | No      | ----      | ----   
| http://download.opensuse.org/debug/update/leap/15.3/non-oss/
 7 | repo-non-oss                | Non-OSS Repository                          
                                               | No      | ----      | ----   
| http://download.opensuse.org/distribution/leap/15.3/repo/non-oss/
 8 | repo-oss                    | Main Repository                             
                                               | No      | ----      | ----   
| http://download.opensuse.org/distribution/leap/15.3/repo/oss/
 9 | repo-sle-debug-update       | Update repository with debuginfo for updates
from SUSE Linux Enterprise 15                  | No      | ----      | ----   
| http://download.opensuse.org/debug/update/leap/15.3/sle/
10 | repo-sle-update             | Update repository with updates from SUSE
Linux Enterprise 15                                | Yes     | (r ) Yes  | Yes 
   | http://download.opensuse.org/update/leap/15.3/sle/
11 | repo-source                 | Source Repository                           
                                               | No      | ----      | ----   
| http://download.opensuse.org/source/distribution/leap/15.3/repo/oss/
12 | repo-update                 | Main Update Repository                      
                                               | Yes     | (r ) Yes  | Yes    
| http://download.opensuse.org/update/leap/15.3/oss
13 | repo-update-non-oss         | Update Repository (Non-Oss)                 
                                               | No      | ----      | ----   
| http://download.opensuse.org/update/leap/15.3/non-oss/