How near to the edge of the cabinet can you drill?
I use kitchen cabinet hanging rail, which comes in 1, 2 or 3 metre lengths, and has screw-holes all the way along, so can bridge over steelwork and buried cables, the cabinets hook on anywhere and can be slid along if you want. It's strong and rigid though I wouldn't want a lot of weight on an end far beyond a screw.
You can run it all along the kitchen wall and it will be level and you can hang the cabs wherever you want.
The 25mm depth you mention is probably just plaster, so no use. It's possible to drill into the steel lintel with an HSS bit, and a self-tapper if it's not very thick. There may be other ways. With hanging rail, the force will be downwards, not pull-out.