Flaring the reveals asymmetrically solved this for us on a heavy retrofit near Tonnerre. Angling the southern jamb gives you a broad scoop of bounced light, and acoustically it breaks up the exterior flutter before it hits the pane.

Have you tried splaying the jambs to bounce the light inward, or are you hoping to solve it with a reflective liner? The warmth you get off an angled reveal is incredible, though trades usually groan the second you taper the insulation.

Asymmetric splayed jambs! Angling just the sun-facing cheek bounces a ton of light back inside and makes that heavy depth look totally intentional.

Are you working with a rendered facade, or do you have the clearance to splay the jambs with an applied lining? Carving that reveal back at a gentle angle changes the daylight bounce completely, though getting the waterproofing clean around the turn is always the rub.

Are you able to splay the jambs at an angle to bounce that daylight inward, or is the cladding subframe forcing you into strict 90-degree returns?

Splaying the jambs even ten or fifteen degrees turns that thickness into an ambient light scoop instead of a shadow box. It catches the low-angle sun beautifully, too.

Splaying the rigid insulation back at a 15-degree angle at the jambs changes everything. We line that deep return with a pale, brake-formed aluminum flashing to catch the low sun and bounce it deep into the room instead of choking it at the glass line.

Are you able to splay the jambs outward to bounce that light in, or is the cladding substructure forcing you into right angles? Curious what material you're trying to wrap into the reveal.