this doesn't seem reproducible with just passing --reverse argument (all is correctly flipped, the search bar doesn't overlap logout button

I'll try to check it on virtual machine with the last KDE Neon later

Hmm it's always possible things bitrot, but I usually do test with rtl ...

I Install KDE Neon on virtual machine
I try:
killall plasmashell
kstart plasmashell --reverse

The search bar still overlap logout button.

and secondly I try to set the system to Hebrew
and the search bar still overlap...

I found the problem and I write a patch:

In plasma-desktop git, applets/kicker/package/contents/ui/MenuRepresentation.qml

Row 62:
LayoutMirroring.enabled: ((plasmoid.location == PlasmaCore.Types.RightEdge)
    || (Qt.application.layoutDirection == Qt.RightToLeft))

Row 353:
the search field:
when: (plasmoid.location == PlasmaCore.Types.RightEdge
    || (plasmoid.location != PlasmaCore.Types.RightEdge && mainRow.LayoutMirroring.enabled))

The idea was if the widget is on the right edge the layout will mirrored (the side bar be on the right - try it and understand)
This cause problem - the search field overlap logout button on RTL lang
Because when the LayoutMirroring.enabled (on LTR when RightEdge and on RTL langs) all the left and right switched
* (363) "anchors.right: parent.right" become "anchors.left: parent.left"
* (368) "anchors.rightMargin: ..." become "anchors.LeftMargin: ..."

So I think and I write patch with this thought:
Like that LTE with RightEdge is mirrored so RTL with LeftEdge should be (not mirrored)

The Patch:

Replace rows 62-63 with:
LayoutMirroring.enabled: ((plasmoid.location == PlasmaCore.Types.RightEdge)
    || (Qt.application.layoutDirection == Qt.RightToLeft && plasmoid.location != PlasmaCore.Types.LeftEdge))

Replace rows 353-354 with:
when: (plasmoid.location == PlasmaCore.Types.RightEdge && Qt.application.layoutDirection == Qt.LeftToRight)
    || (plasmoid.location == PlasmaCore.Types.LeftEdge && Qt.application.layoutDirection == Qt.RightToLeft)

I tried the patch on my system and check LTR and RTL with right and left edged panels

Can you apply the patch?

I found out how to do it myself...

https://phabricator.kde.org/D3553

Please only close this once the patch is committed.

Committed
https://phabricator.kde.org/D3553