Hi all, 
in the meantime I posted the install issue on Barry Kauler´s forum ( EasyOS 32-bit Dunfell-series version 4.3.2 - Puppy Linux Discussion Forum ) and after a bit of work I got EasyOS running in my vm:
- note: good instructions here: How to write EasyOS to a flash drive
- Debian10 is already installed in the vm (virt-manager/qemu/kvm)
- I downloaded easydd from http://bkhome.org/files/easydd.gz , unpacked it and set the correct permissions. Easydd is a frontend for
dd. It´s a clever script as it turned out
- performing sudo
./easydd easy-4.3-4-amd64.img(the script asked about the drive I wanted to write to beforehand) - so this isn´t going to work with ventoy (at least not for the latest version of EasyOS).
Therefore I needed a dedicated stick for EaysOS alone. - After the write was complete I chose in the settings of my Debian vm: “add device”
- I chose “USB host-device” and from the popup menu the respective stick
- in “boot options” this is the boot order: the usb-stick - VirtIO - NIC
- ( topic also dealt with in Virt-manager: redirection of USB-stick )
- the vm boots EasyOS from the stick
All that worked well in the end 
.
Yet the running EasyOS presents another problem:
I cannot connect to the internet. 
Although EasyOS is supposed to automatically recognize available network devices it doesn´t seeem to…
When running Debian in the vm it automatically connects to the virtual LAN. BodhiLinux as well. So theoretically there shouldn´t be any problems. 
No idea why EasyOS cannot do the same…
Many greetings from Rosika