Done loads of different mountings over the years, it really depends on the overall environment.
For commercially, ideally a purpose built "farm environment" where the ground is concrete, there is no vegetation within a mile, lol, you can run all containment in nice neat runs. A/C units mounted above anticipated snow level, nice spacing between them for servicing, easy access for lugging heavy cylinders and pumps for servicing. Units are bolted to the ground on raised pads.
I have used the custom brackets that can be bought from a/c wholesalers but have found they are largely powder coated steel, over time the coating fails and the brackets go rusty. There advantage is that they are easy to fit for smaller units as there is just a horizontal plate which the cantelever brackets clip onto.
My favourite is unistrut and their ready made cantelever brackets, use M12 Zebs and they can easily take the weight of the largest units. You can get covers and cap ends for unistrut and it does not look too bad for domestic, especially if you size the verticals no higher than the top of the outdoor unit and just a couple of inches below the bracket. Often use resin as well as rawl bolts when i think the bricks/blocks are too brittle.
For the really heavy units 100KG, etc i run the unistrut verticals down to the ground and use ground plates to take the vertical load and rawl bolts into brick/block.
I have used the big foot system
Big Foot Systems Aircon Spares | Air Conditioning Replacement Parts - https://www.airconspares.com/brands/big-foot-systems
But its rare as you are trying to reduce the movement of the outdoor units relative to the pipework, otherwise you can get leaks on the larger 5/8inch pipes and above that dont like to move much.