Problem while installing NitrokeyPro's App

[stebe at mailbox.org]

Hi GnuPG users,

(sorry for this long posting)
I'm about to create a new key using NitrokeyPro and its app but I have
some problems with installing the app.
I am not sure if this is more a Nitrokey or a Debian issue. I'm using
Debian oldstable (7.9.) 32 bits on a 64 bit processor and a 64 bit kernel.

The app is only available as a 64 bit version for jessieamd64. I first
considered compiling a 32 bit version for my needs, but then I
accidentally learned (1) that the i386 version of i386 has a (basic)
support for running 64bit third-party binaries. At least in (1) it is
indicated that there is such a "minmilastic runtime support".

sudo dpkg -i nitrokey-app-0.2-debian-jessie-amd64.deb && apt-get install
-f
resulted in 
(original in German; configuration failed due to dependency issues)
Entpacken von nitrokey-app (aus nitrokey-app-0.2-debian-jessie-amd64.deb)
...
dpkg: Abhängigkeitsprobleme verhindern Konfiguration von nitrokey-app:
 nitrokey-app hängt ab von libappindicator1.
 nitrokey-app hängt ab von libnotify4.
 nitrokey-app hängt ab von libqt5widgets5.
 nitrokey-app hängt ab von libqt5gui5.
 nitrokey-app hängt ab von libqt5core5a.

So I updated my sources.list with wheezy-backports, eager to install the
lacking dependencies libqt5widgets5, libqt5gui5, libqt5core5a from there,
but that did not help. libappindicator1 and libnotify4 were already
installed on my oldstable system, but the app, as one can see in the
output above, ignored them, i.e. maybe needs another version (I installed
all these 5 dependencies first as 32 bits, thinking that if the 64 bit app
accepted all the other 32 bit stuff it now will only need the 32 bit
version of them. I was still thinking that the referred i386 support for
64bit 3rd party binaries could be enabled by this.

I ran 
sudo dpkg -i nitrokey-app-0.2-debian-jessie-amd64.deb && apt-get install
-f
again, but again

(original in German)
Entpacken von nitrokey-app (aus nitrokey-app-0.2-debian-jessie-amd64.deb)
...
dpkg: Abhängigkeitsprobleme verhindern Konfiguration von nitrokey-app:
 nitrokey-app hängt ab von libappindicator1.
 nitrokey-app hängt ab von libnotify4.
 nitrokey-app hängt ab von libqt5widgets5.
 nitrokey-app hängt ab von libqt5gui5.
 nitrokey-app hängt ab von libqt5core5a.

In a desperate attempt to solve the issue :-) I did a 
dpkg --add-architecture amd64 
to do the best possible to have the dependencies installed, if not in a 32
bit version (ignored by the app), using the 64 bit versions in backports
and oldstable, respectively: this damned app should run with it, I
thought! But then there were even more dependency issues, requiring me to
install even more 64 bit packages to solve even more dependency problems.
I told apt to resolve the dependency issues (even if it had to install all
that bunch of 64 bit versions of the dependencies of the app's
dependencies) but apt's output was that it was not possible to get the
dep. issues resolved. :-(

Any ideas how to solve this within 32 bit oldstable? Is it better to post
it on a Debian specific forum/mailing list? Or to upgrade right away to 64
bit jessie using apt --dist-upgrade? 

Any ideas welcome.

Cheers,
Stebe

(1) https://www.debian.org/ports/amd64/index.en.html