The UNO command ".uno:UnhainFrames" seems to bear a typo. https://opengrok.libreoffice.org/xref/core/officecfg/registry/data/org/openoffice/Office/UI/WriterCommands.xcu?r=6320a4c2#2639 and, in /workdir/SdiTarget/sw/sdi/swslots.hxx we have // Slot Nr. 59 : 21737 SFX_NEW_SLOT_ARG( SwFrameShell,FN_FRAME_UNCHAIN,SfxGroupId::Frame, &aSwFrameShellSlots_Impl[1] /*Offset Next*/, SFX_STUB_PTR(SwFrameShell,Execute),SFX_STUB_PTR(SwFrameShell,GetState), SfxSlotMode::AUTOUPDATE|SfxSlotMode::RECORDPERSET|SfxSlotMode::MENUCONFIG|SfxSlotMode::TOOLBOXCONFIG|SfxSlotMode::NONE, SfxDisableFlags::SwOnProtectedCursor, SfxVoidItem, 20/*Offset*/, 0, SfxSlotMode::NONE,"UnhainFrames" ),
Just Opengroking, I could confirm this.
I gave a try with https://gerrit.libreoffice.org/c/core/+/158328 but hope we can do this and not stuck because of existing profile or anything.
Finally added in https://wiki.documentfoundation.org/Development/stuck_stuff I can't help here so unassign myself.