I am renovating the kitchen myself. I have putty on the walls and the plasterboard box and will put tiles on the apron, but I have heard the opinion that tiles cannot be put on putty. Is this true?
You can not put the tiles on the putty, it can not withstand the weight and the entire layer, along with the tiles will fall off the wall.
Do not tile over putty.
Clean the area for the apron and make notches into the wall, prime the area and then tile.
Of course it is better to remove the putty, but if you're too lazy to do it, make a couple of coats of primer deep penetration, it helps to strengthen the putty.
But again, to avoid problems in the future, remove the putty before you lay the tiles.