Change:
// Register default debug views const viewsRegistry = Registry.as<IViewsRegistry>(ViewExtensions.ViewsRegistry); <del> viewsRegistry.registerViews([{ id: VARIABLES_VIEW_ID, name: nls.localize('variables', "Variables"), containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(VariablesView), order: 10, weight: 40, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusVariablesView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: WATCH_VIEW_ID, name: nls.localize('watch', "Watch"), containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(WatchExpressionsView), order: 20, weight: 10, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusWatchView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: CALLSTACK_VIEW_ID, name: nls.localize('callStack', "Call Stack"), containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(CallStackView), order: 30, weight: 30, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusCallStackView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: BREAKPOINTS_VIEW_ID, name: nls.localize('breakpoints', "Breakpoints"), containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(BreakpointsView), order: 40, weight: 20, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusBreakpointsView' }, when: ContextKeyExpr.or(CONTEXT_BREAKPOINTS_EXIST, CONTEXT_DEBUG_UX.isEqualTo('default')) }], viewContainer); viewsRegistry.registerViews([{ id: WelcomeView.ID, name: WelcomeView.LABEL, containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(WelcomeView), order: 1, weight: 40, canToggleVisibility: true, when: CONTEXT_DEBUG_UX.isEqualTo('simple') }], viewContainer); viewsRegistry.registerViews([{ id: LOADED_SCRIPTS_VIEW_ID, name: nls.localize('loadedScripts', "Loaded Scripts"), containerIcon: 'codicon-debug-alt-2', ctorDescriptor: new SyncDescriptor(LoadedScriptsView), order: 35, weight: 5, canToggleVisibility: true, canMoveView: true, collapsed: true, when: ContextKeyExpr.and(CONTEXT_LOADED_SCRIPTS_SUPPORTED, CONTEXT_DEBUG_UX.isEqualTo('default')) }], viewContainer); </del> <ins> viewsRegistry.registerViews([{ id: VARIABLES_VIEW_ID, name: nls.localize('variables', "Variables"), containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(VariablesView), order: 10, weight: 40, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusVariablesView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: WATCH_VIEW_ID, name: nls.localize('watch', "Watch"), containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(WatchExpressionsView), order: 20, weight: 10, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusWatchView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: CALLSTACK_VIEW_ID, name: nls.localize('callStack', "Call Stack"), containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(CallStackView), order: 30, weight: 30, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusCallStackView' }, when: CONTEXT_DEBUG_UX.isEqualTo('default') }], viewContainer); viewsRegistry.registerViews([{ id: BREAKPOINTS_VIEW_ID, name: nls.localize('breakpoints', "Breakpoints"), containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(BreakpointsView), order: 40, weight: 20, canToggleVisibility: true, canMoveView: true, focusCommand: { id: 'workbench.debug.action.focusBreakpointsView' }, when: ContextKeyExpr.or(CONTEXT_BREAKPOINTS_EXIST, CONTEXT_DEBUG_UX.isEqualTo('default')) }], viewContainer); viewsRegistry.registerViews([{ id: WelcomeView.ID, name: WelcomeView.LABEL, containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(WelcomeView), order: 1, weight: 40, canToggleVisibility: true, when: CONTEXT_DEBUG_UX.isEqualTo('simple') }], viewContainer); viewsRegistry.registerViews([{ id: LOADED_SCRIPTS_VIEW_ID, name: nls.localize('loadedScripts', "Loaded Scripts"), containerIcon: Codicon.debugAlt.classNames, ctorDescriptor: new SyncDescriptor(LoadedScriptsView), order: 35, weight: 5, canToggleVisibility: true, canMoveView: true, collapsed: true, when: ContextKeyExpr.and(CONTEXT_LOADED_SCRIPTS_SUPPORTED, CONTEXT_DEBUG_UX.isEqualTo('default')) }], viewContainer); </ins> registerCommands();

Discussion:
Today I see no debug icon in the activity bar.
Yeah, I also can't see !
Removed in Looks like not longer in font and has different character code but it's actually in font
Sorry about that, I must've copied the wrong unicode character when I was cleaning up the unused debug icons. Looking into PR right now.