I would create a meadow there (Magerwiese, Blumenwiese), not a lawn. You can let it "go wild".
Perennial bed with ground cover, prairie garden, rock garden (real ones and not gravel with 3 green bushes).
With the gravel with 3 green bushes, you have the problem of keeping it clean. Leaves, needles, pollen, street dirt. Especially the latter should not be underestimated on the main street.
I might also replace the hedge. It depends on how healthy it still is. Either you take Thuja again or you take ones that are declared as bird protection hedges, bee hedges, four seasons hedges. Then something always blooms.
Consider where you want a wall or a fence because of children and/or dog or where open.
My "front garden" will get an approximately 80 sqm prairie bed. On the one hand, the soil is quite stony, on the other hand, something is always blooming and in about 2 years it should be quite low maintenance. Pruning and thinning in spring and autumn, no watering, no weeding.
I will report whether it works. I hope I can create it this year.