I've got one of the 868Mhz Meshcore repeaters with the 5.5db 40cm antenna but it came with a pole mount bracket and I needed wall mount. I've made this wall mounting bracket with an offset to hold it away from the wall and up a bit so that it can get around roof lines and keep the antenna up in clear air.

It's intended to use 3 5mm x 40mm screws and plastic plugs to mount to the wall and to screw to the repeater with the supplied screws. It's got cable-tie mounting points on the arms and is designed to shed water away from the wall to hopefully prevent it causing issues with damp.