Looking for help as I'm struggling with upgrading my system (tumbleweed, kde6)

[OrsoBruno]

@boredcollie

#  | Alias                            | Name                                                 | Enabled | GPG Check | Refresh | Priority | Type   | URI                                                                                         | Service
---+----------------------------------+------------------------------------------------------+---------+-----------+---------+----------+--------+---------------------------------------------------------------------------------------------+--------
 1 | ROCm-6.0                         | ROCm6.0                                              | Yes     | (r ) Yes  | No      |   99     | rpm-md | https://repo.radeon.com/rocm/zyp/6.0/main                                                   | 
 2 | amdgpu                           | amdgpu                                               | Yes     | (r ) Yes  | No      |   99     | rpm-md | https://repo.radeon.com/amdgpu/6.0/sle/15.5/main/x86_64/ 

You need help from an experienced AMD user, but the two AMD repos you currently have are for SLE 15.5 and not for Tumbleweed: they are compatible with the 6.0.x kernel apparently, while TW is currently at 6.8.x.
Easy guess that your “black screen” is due to a graphics driver not compatible with the current kernel and those two AMD repos should be disabled.
You may also keep an old working kernel to boot in case of trouble, but that is a workaround and not a long term solution.