How do i get Scilab 6.1.0 working on ubuntu 20.04?

I've installed the ubuntu repo of Scilab 6.1.0 and ive been trying to run it, The error message i get is

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.scilab.modules.jvm.LibraryPath ?(file:/usr/share/scilab/modules/jvm/jar/org.scilab.modules.jvm.jar) to field java.lang.ClassLoader.sys_paths
WARNING: Please consider reporting this to the maintainers of org.scilab.modules.jvm.LibraryPath
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Could not access to the Main Scilab Class:
Exception in thread "main" java.lang.ExceptionInInitializerError
	at org.scilab.modules.localization.Messages.gettext(Unknown Source)
	at org.scilab.modules.commons.xml.XConfiguration.<clinit>(Unknown Source)
	at org.scilab.modules.core.Scilab.<clinit>(Unknown Source)
Caused by: java.lang.NullPointerException
	at java.base/java.lang.ClassLoader.loadLibrary(ClassLoader.java:2646)
	at java.base/java.lang.Runtime.loadLibrary0(Runtime.java:830)
	at java.base/java.lang.System.loadLibrary(System.java:1870)
	at org.scilab.modules.localization.MessagesJNI.<clinit>(Unknown Source)
	... 3 more

Scilab cannot create Scilab Java Main-Class (we have not been able to find the main Scilab class. Check if the Scilab and thirdparty packages are available).

I have tried:

• running from the cli
• running from the launcher

the cli version works

have gone to the forums and checked for the different solutions

• deleting the SCIHOME directory.
• reinstalling Scilab.
• reinstalling from different sources.
• purging all the directories related to Scilab and reinstalling.

The Ubuntu package is broken. Please use the official .tar.gz distribution from Scilab site: https://www.scilab.org/download/6.1.0

If it says that libtinfo.so.5 file is not available, run the following command in the terminal :

sudo ln -s /usr/lib/x86_64-linux-gnu/libtinfo.so.6 /usr/lib/x86_64-linux-gnu/libtinfo.so.5

The broken package is best fixed by rebuilding the scilab package from ubuntu groovy on your ubuntu focal machine and installing the generated deb files.

This can be done as follows:

create a folder for the build process:

mkdir scilab-focal
cd scilab-focal

Make certain we have everything on your system:
Enable the deb-src lines in /etc/apt/sources.list and Install wget and apt-src if not yet installed

sudo sed -i s/#\ deb-src/deb-src/g /etc/apt/sources.list  
sudo apt update && apt install -yy wget apt-src && apt-src update

download the following scilab source packages from ubuntu groovy:

wget http://archive.ubuntu.com/ubuntu/pool/universe/s/scilab/scilab_6.1.0+dfsg1-6build2.dsc
wget http://archive.ubuntu.com/ubuntu/pool/universe/s/scilab/scilab_6.1.0+dfsg1.orig.tar.xz
wget http://archive.ubuntu.com/ubuntu/pool/universe/s/scilab/scilab_6.1.0+dfsg1-6build2.debian.tar.xz

extract the scilab packages as required for the automated build process:

tar xf scilab_6.1.0+dfsg1.orig.tar.xz
cd scilab-6.1.0
tar xf ../scilab_6.1.0+dfsg1-6build2.debian.tar.xz

Build and install scilab

apt-src import --here .
apt-get build-dep -yy scilab    
apt-src build -i -k scilab

Hope this helps anybody trying to get scilab 6.1.0 working on ubuntu focal!

linking libtinfo.so.5 file is first step of the solution. But still scilab can not plot or show any graphics. One possible way is to run the scilab with

LIBGL_ALWAYS_SOFTWARE=1 scilab

command. I have tried this and solve the same issue of scilab with Ubuntu 22.04 LTS. Dont know, why this works. Still looking for permanent solution..