I just published my holder design for SKR 1.4 Turbo board for mirrored Bear Upgrade. Although this would work in non-mirrored setup, or any setup that has 2040 aluminium rail and needs to have board with SKR 1.4 dimensions mounted to it.
https://www.printables.com/model/230859-skr-14-turbo-mount-for-bear-upgrade-2040-rail
I've been testing this design my 3D printer running with that board for so long, I forgot I had it in drafts.