Guys, after some time, I today needed to start Digikam, version 7.2.0.
Unfortunately it won’t start, I get this error when trying to launch Digikam from a terminal:
digikam: symbol lookup error: /usr/lib/libdigikamcore.so.7.2.0: undefined symbol: _ZN2cv3dnn14dnn4_v202011178NMSBoxesERKSt6vectorINS_5Rect_IiEESaIS4_EERKS2_IfSaIfEEffRS2_IiSaIiEEfi
Any ideas?
J.
It is a library mismatch. Report it upstream.
It was just rebuilt upstream, could be the same issue.
Update your system.
My system is up to date. Still, Digikam won’t start.
J.
Don’t think it has hit the repo yet.
I also had this issue, after some research (by using Timeshift and then updating each package since yesterday one at a time) I found out it is the recent opencv 4.5.2-1 is causing the issue. Downgrading the package will start Digikam again.
I guess Digikam will release an update soon.
not the solution, but for the moment:
https://download.kde.org/stable/digikam/7.2.0/digiKam-7.2.0-x86-64.appimage.mirrorlist
I have actually been using the digikam appimage for years to avoid all the digikam dependencies. It works pretty well.
indeed.
with time, i have started to replace all large packages that i use rarely, with appimages - less trouble and saves time with updates.
Beat me to it 
Indeed, Digikam works again.
Issue solved, thanks to everybody for your assistance.
J