I successfully installed Version 5.2.1 - f99804 and after some minor reconfiguration successfully loaded up my home accounts  database (which does not utilise Tags).
I then loaded my charity database which makes extensive use of Tags for management and reporting. I was able to make a new entry including the corresponding Tags.
I later checked other entries and there were no tags displayed at all. I checked "Your Tags" and they were all present including the ones associated with the new entry I made.
After some experimentation  (unsuccessful)  (I tried Version 5.2.1-0683f36 too), I decided to revert to Version 5.1.3 and uninstalled KMyMoney.
After installation of 5.1.3, I loaded both my home accounts and charity accounts from databases saved under 5.2.1 and verified that the expected data was there. I especially checked that the tags were displayed and I can confirm that all tags were present including those created under Version 5.2.1.

SUMMARY
Version 5.2.1 Ledger view fails to display tags created under Version 5.1.3

STEPS TO REPRODUCE
1. As described above
2. 
3. 

OBSERVED RESULT
As above

EXPECTED RESULT
As Above

SOFTWARE/OS VERSIONS
Windows: 11 23H2
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 
KDE Frameworks Version: N/K
Qt Version: 

ADDITIONAL INFORMATION