Strange Observations

1- Shortly after trying SH3D and getting the above problem, I ran out of disk space.
After investigation (du -hsx /var/log | sort -rh | head -10), I found out that syslog had
swelled to 62G. I had to purge syslog to avoid formatting. This has not occurred since.
2- A similar ...

Running as root returns the same result.

Submitted a bug report in Launchpad:
Bug #2139244 “Null Pointer Exception in Sweet Home 3D Design Sof...” : Bugs : ubuntu-release-upgrader package : Ubuntu

Thanks Dorin and Keet but SH3D still doesn't work with KDE

Latest trial

Download Java 8 for Linux x64 from https://www.java.com/fr/download/linux_manual.jsp

sudo mkdir /usr/java
sudo mv ~/Téléchargements/jre-8u481-linux-x64.tar.gz /usr/java
cd /usr/java
sudo tar zxvf jre-8u481-linux-x64.tar.gz ...

Thanks for the prompt response.
Definitely SweetHome3D does not work under KDE Plasma,
but it works fine under MX-Linux 25 with XFCE on a HP Probook.

===============================================================
Purge of Directories and reinstall under KDE-Plasma

apt list sweet* > SH3D_purge ...

I installed SW3D from the latest website version. I tried fom the desktop icon and the terminal and got a Null Pointer Exception (see output below).

I was running version 7.5 on the same machine under Debian_MX-Linux 21 with XFCE without problem.
I tried the snap version from the Ubuntu repository ...