Here is a patch that brings back LMB actions when the applets are locked. With unlocked applets LMB is needed for editing, and I didn't want to spend too much time on it. Read here for some discussion: https://phabricator.kde.org/D24748 But better than nothing, isn't it? ;)
Place it into /etc/portage/patches/kde-plasma/plasma-workspace/ and reemerge plasma-workspace.
--- plasma-workspace-5.17.4/components/containmentlayoutmanager/appletslayout.cpp.org 2020-01-04 08:43:18.958318856 +0200 +++ plasma-workspace-5.17.4/components/containmentlayoutmanager/appletslayout.cpp 2020-01-04 08:51:56.229879126 +0200 @@ -530,6 +530,11 @@ void AppletsLayout::mousePressEvent(QMouseEvent *event) { + if (!m_editMode && m_editModeCondition == AppletsLayout::Locked) { + event->setAccepted(false); + return; + } + forceActiveFocus(Qt::MouseFocusReason); if (!m_editMode && m_editModeCondition == AppletsLayout::Manual) {