I am experiencing the same problem.

Pentaho CE 10.2.0.0-222 / JDK 17.0.10

Action: Open file - Browse a subdir from root dir ("/")

Error:

Exception occurred
java.lang.NullPointerException: Cannot invoke "org.pentaho.di.repository.RepositoryDirectoryInterface.getName()" because "repositoryDirectoryInterface" is null
    at org.pentaho.di.plugins.fileopensave.providers.repository.model.RepositoryDirectory.build(RepositoryDirectory.java:43)
    at org.pentaho.di.plugins.fileopensave.providers.repository.RepositoryFileProvider.getFiles(RepositoryFileProvider.java:107)
    at org.pentaho.di.plugins.fileopensave.providers.repository.RepositoryFileProvider.getFiles(RepositoryFileProvider.java:69)
    at org.pentaho.di.plugins.fileopensave.controllers.FileController.getFiles(FileController.java:131)
    at org.pentaho.di.plugins.fileopensave.dialog.FileOpenSaveDialog$FileTreeContentProvider.lambda$getChildren$0(FileOpenSaveDialog.java:2464)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:74)
    at org.pentaho.di.plugins.fileopensave.dialog.FileOpenSaveDialog$FileTreeContentProvider.getChildren(FileOpenSaveDialog.java:2462)
    at org.eclipse.jface.viewers.AbstractTreeViewer.getRawChildren(AbstractTreeViewer.java:1434)
    at org.eclipse.jface.viewers.TreeViewer.getRawChildren(TreeViewer.java:350)
    at org.eclipse.jface.viewers.StructuredViewer.getFilteredChildren(StructuredViewer.java:852)
    at org.eclipse.jface.viewers.AbstractTreeViewer.getSortedChildren(AbstractTreeViewer.java:626)
    at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:828)
    at org.eclipse.jface.viewers.TreeViewer.createChildren(TreeViewer.java:604)
    at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:779)
    at org.eclipse.jface.viewers.AbstractTreeViewer.setExpandedState(AbstractTreeViewer.java:2526)
    at org.pentaho.di.plugins.fileopensave.dialog.FileOpenSaveDialog.lambda$createFilesBrowser$21(FileOpenSaveDialog.java:1273)
    at org.eclipse.jface.viewers.StructuredViewer$3.run(StructuredViewer.java:823)
    at org.eclipse.jface.util.SafeRunnable$1.run(SafeRunnable.java:129)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:174)
    at org.eclipse.jface.viewers.StructuredViewer.firePostSelectionChanged(StructuredViewer.java:820)
    at org.eclipse.jface.viewers.StructuredViewer.handlePostSelect(StructuredViewer.java:1193)
    at org.eclipse.swt.events.SelectionListener$1.widgetSelected(SelectionListener.java:84)
    at org.eclipse.jface.util.OpenStrategy.firePostSelectionEvent(OpenStrategy.java:263)
    at org.eclipse.jface.util.OpenStrategy.access$5(OpenStrategy.java:258)
    at org.eclipse.jface.util.OpenStrategy$1.lambda$1(OpenStrategy.java:428)
    at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:40)
    at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:132)
    at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4029)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3645)
    at org.eclipse.jface.window.Window.runEventLoop(Window.java:823)
    at org.eclipse.jface.window.Window.open(Window.java:799)
    at org.pentaho.di.plugins.fileopensave.dialog.FileOpenSaveDialog.open(FileOpenSaveDialog.java:322)
    at org.pentaho.di.plugins.fileopensave.extension.FileOpenSaveExtensionPoint.callExtensionPoint(FileOpenSaveExtensionPoint.java:74)
    at org.pentaho.di.core.extension.ExtensionPointMap.callExtensionPoint(ExtensionPointMap.java:142)
    at org.pentaho.di.core.extension.ExtensionPointHandler.callExtensionPoint(ExtensionPointHandler.java:36)
    at org.pentaho.di.ui.spoon.Spoon.openFileNew(Spoon.java:4706)
    at org.pentaho.di.ui.spoon.Spoon.openFileNew(Spoon.java:4670)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.pentaho.ui.xul.impl.AbstractXulDomContainer.invoke(AbstractXulDomContainer.java:309)
    at org.pentaho.ui.xul.impl.AbstractXulComponent.invoke(AbstractXulComponent.java:153)
    at org.pentaho.ui.xul.impl.AbstractXulComponent.invoke(AbstractXulComponent.java:137)
    at org.pentaho.ui.xul.swt.tags.SwtToolbarbutton.access$000(SwtToolbarbutton.java:44)
    at org.pentaho.ui.xul.swt.tags.SwtToolbarbutton$1.widgetSelected(SwtToolbarbutton.java:92)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:252)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
    at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4256)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1066)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4054)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3642)
    at org.pentaho.di.ui.spoon.Spoon.readAndDispatch(Spoon.java:1429)
    at org.pentaho.di.ui.spoon.Spoon.waitForDispose(Spoon.java:8217)
    at org.pentaho.di.ui.spoon.Spoon.start(Spoon.java:9586)
    at org.pentaho.di.ui.spoon.Spoon.main(Spoon.java:735)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at org.pentaho.commons.launcher.Launcher.main(Launcher.java:88)

Thanks in advance for any support