I am inclined to put it in the ‘too hard’ basket. Both Plantnet and the Vicflora key separates gracilis from subtilis: gracilis with bristly stems, the fine rigid hairs about 0.5 mm long, and leaves narrow ovate or linear and 1.5-4 mm wide; subtilis - stem hairs very short about 0.1 mm long, and linear leaves mostly 0.6-2 mm wide. What you report partially fits both of them.