No pictures shown with Digikam 9.1.0 and Kubuntu 25.10

Dear Digikam Developers :),

I recently switched from Windows to Linux and as photography is one of my=
=20
hobbies, I decided to contribute to Digikam even if I've never developed a=
n=20
application SW before. At least I have some ideas coming from a very power=
ful=20
windows tool :)

Currenty I'm working as a systems engineer for product safety for power=20
electronics but in the past I also worked as a SW-developer for embedded=
=20
systems where I mainly used C for around 5 years. Besides of that I do=20
scripting (perl, python, java) here and there and a some smart home stuff =
if=20
there is some free time between family and work. So I think I could be abl=
e to=20
contribute :)

To start developing I set up a clean install of Kubuntu 25.10, installed Q=
T=20
6.10.2 via the QT installer incl. dependencies and finally used kde-builde=
r to=20
build the latest version of Digikam. And - suprise - Digikam 9.1.0 is runn=
ing.=20
But unfortunately I can not open/show pictures.

I added a picture folder in my home directory as a new collection and the=
=20
preview pictures are shown, I can tag them, filter, search... all is worki=
ng.=20
But if I try to open a picture (e.g. double click), I only get a message i=
n=20
the main window "Bild kann nicht geladen werden" ("Can not load picture").=
=20

The terminal says the following if I try to open a picture (the Epson is m=
y=20
printer that is automatically detected by Kubuntu):
digikam.dimg: ICM Wayland: the device is not a screen: "/org/freedesktop/
ColorManager/devices/cups_EPSON_ET_8550_Series"
QPainter::begin: Paint device returned engine =3D=3D 0, type: 2
QPainter::begin: Paint device returned engine =3D=3D 0, type: 2

At the moment I don't even know whether this is a fault message or not but=
 I=20
assume that showing pictures should work with V 9.1.0 even if it's in=20
development. At least I would prefer to start with a baseline for which th=
e=20
core functions are working...

Can you give me some advice where I coud start troubleshooting? Is it Kubu=
ntu?=20
Is it the build with kde-builder? Is there some better platform to discuss=
=20
such topics?

What I already did, was to build V9.0.0 with the tag option of kde-builder=
 but=20
the result was the same.

Looking forward for your replies!=20

Regards,

Jens