I cannot inspect the workspace on MATLAB for linux

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I have an issue running MATLAB 2020a on Ubuntu 20.04. MATLAB starts up properly but it shows the

PostVMInit failed to initialize com.mathworks.mwswing.MJStartupForDesktop

message.

Then, when I want to inspect a variable all I get is a series of errors, e.g.:

Exception in thread "AWT-EventQueue-0": java.lang.NoClassDefFoundError: Could not initialize class com.mathworks.mwswing.MJStartupForDesktop
	at com.mathworks.mwswing.MJStartup.init(MJStartup.java:95)
	at com.mathworks.mwswing.MJStartup.init(MJStartup.java:72)
	at com.mathworks.widgets.spreadsheet.SpreadsheetColor.<clinit>(SpreadsheetColor.java:58)
	at com.mathworks.widgets.spreadsheet.SpreadsheetTable.setupColorHandlers(SpreadsheetTable.java:314)
	at com.mathworks.widgets.spreadsheet.SpreadsheetTable.<init>(SpreadsheetTable.java:198)
	at com.mathworks.mlwidgets.array.AbstractMatlabTable.<init>(AbstractMatlabTable.java:65)
	at com.mathworks.mlwidgets.array.ArrayTable.<init>(ArrayTable.java:102)
	at com.mathworks.mlwidgets.array.ArrayEditorProvider.createProvider(ArrayEditorProvider.java:55)
	at com.mathworks.mlwidgets.array.ValueEditorProviderRegistry.getArrayViewer(ValueEditorProviderRegistry.java:402)
	at com.mathworks.mlwidgets.array.ValueEditorProviderRegistry.getValueEditorProvider(ValueEditorProviderRegistry.java:83)
	at com.mathworks.mlwidgets.array.ValuePanel$UpdateListener.actionPerformed(ValuePanel.java:221)
	at com.mathworks.mlwidgets.array.ValueMetaInfoRequester$VICO.matlabEvent(ValueMetaInfoRequester.java:143)
	at com.mathworks.jmi.MatlabMCR$AWTReplyEvent.run(MatlabMCR.java:1641)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Exception in thread "AWT-EventQueue-0": java.lang.NoClassDefFoundError: Could not initialize class com.mathworks.widgets.spreadsheet.SpreadsheetColor
	at com.mathworks.widgets.spreadsheet.SpreadsheetTable.setupColorHandlers(SpreadsheetTable.java:314)
	at com.mathworks.widgets.spreadsheet.SpreadsheetTable.<init>(SpreadsheetTable.java:198)
	at com.mathworks.mlwidgets.array.AbstractMatlabTable.<init>(AbstractMatlabTable.java:65)
	at com.mathworks.mlwidgets.array.ArrayTable.<init>(ArrayTable.java:102)
	at com.mathworks.mlwidgets.array.ArrayEditorProvider.createProvider(ArrayEditorProvider.java:55)
	at com.mathworks.mlwidgets.array.ValueEditorProviderRegistry.getArrayViewer(ValueEditorProviderRegistry.java:402)
	at com.mathworks.mlwidgets.array.ValueEditorProviderRegistry.getValueEditorProvider(ValueEditorProviderRegistry.java:83)
	at com.mathworks.mlwidgets.array.ValuePanel$UpdateListener.actionPerformed(ValuePanel.java:221)
	at com.mathworks.mlwidgets.array.ValueMetaInfoRequester$VICO.matlabEvent(ValueMetaInfoRequester.java:143)
	at com.mathworks.jmi.MatlabMCR$AWTReplyEvent.run(MatlabMCR.java:1641)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

From this moment ANY command window output is followed by a series of error meassages of this type:

    Exception in thread "AWT-EventQueue-0": java.lang.NoClassDefFoundError: Could not initialize class com.mathworks.widgets.spreadsheet.SpreadsheetColor

I don't know if it's related, but MATLAB starts with SOTWARE OPENGL rendering.

NOTE: If I run MATLAB as root the problem is gone!

Non-successfull solutions tried:

I alried tried to erase preferences (Solution#1 from this answer)

I tried to use the system's JVM (openjdk 8) setting the MATLAB_JAVA variable accordingly.

None of the solutions from this answer worked