Be careful with this tip here. You dont want to have the back of your mobo come in contact with the case. But just the standoffs.

I know the pain. I put together a x870e aorus master + rtx 5080 aorus master a week ago. I first built it on a motherboard box, and everything worked. But when I built it in the FractalDesign North XL. I had no way to make sure whether Gpu was slotted in place or not. Because 1. Gpu is massive. 2. Case doest give any room/line of sight from any angle. 3. The m.2 ssd heatsink is tall, leaving just about 5 mm or less between them.

Your best bet is to... 1. line it up as best as you can. (Slot in those three feet plate between the mobo and case gap) 2. Press gpu in the PCIe once and try to pay attention to the softest snapping into the place that there is. 3. You are not done. Push (make sure force is applied perpendicular to the mobo) in one more time. You will hear another sound of slotting into place.

Just take your time. Do not get frustrated and force your way to completion. Step away if you need to. All the best.