Crankarm hitting frame - BB-R60 with GRX 1x11 Hybrid - Gravel conversion

If it's a steel frame, then adding indentation on the left side is a solution, albeit an advanced one that needs to be done with care. A good way to do it at home is use a piece of wood and a rasp/file to create a support form for the inside of the chainstay, tape that to one vise jaw, tape a socket lengthwise to the other vise jaw, and squish. The way they do it at factories is not particularly any more sophisticated. A good rule of thumb type minimum gap to avoid rub under load is 3mm, so in other words you're doing 2mm to eliminate the interference and then another 3 to accomodate flex. Measure the frame OLD beforehand and then if it changes, align the frame afterward with a 2x4 and string. Standard caution that yes you can destroy the bike doing this kind of thing.

If it's not a steel frame there is no solution.

There are no spacer tricks you can play with Shimano road cranks because you can't compromise the left side spline engagement by any amount, and certainly not by the amount you would need here to both eliminate the interference and then create the aforementioned gap. Not safe, risks ruining the cranks and/or having the arm fall off etc. The BB is intended to use without any spacers, so there is no swapping or adding spacers to offset it. (In other words, yes you could create clearance by adding spacers under the left side cup or on the spindle itself, but there will be inadequate contact surface between the spindle and the crank with any such solution.)