Only after dismantling this protective casing, the video card was installed on the motherboard.
If the EVGA engineers would not make these stiffeners at all, or if their direction was not in the direction of the motherboard but from it, then there would be no problems with the installation.
Due to the fact that I installed the water block, I managed to see the reason before the protective cover would get destroyed. With the native air cooling system, these obstacles would not be visible.

 

Probably it works if the case allows. In my case, such a stock does not move, and I did not have the opportunity to move the motherboard a sufficient distance before the final fixation. Just not quite clear what guided the engineers who decided that the ribs should certainly look inside the case? While nothing prevented to place them in the direction from outside the case. As a result, the user who does not know the cause of the problem will attempt to install the video card as a result of the installation and damage the protective casing of the motherboard, which may lead to the fact that it may have problems in case of any contact with RMA in the Asus. Also, when resale on "second hand" damaged cover will adversely affect the cost of the motherboard and the reputation of the seller.

You are absolutely right - it is made to protect from sagging. But I am sure that if this stiffener were located in the direction from outside the computer case, there would be an equivalent effect of protecting the holder fastening straps from deformation. On the one hand, Asus can be blamed for the fact that for unknown reasons, he made an absolutely non-functional "cutout" on the protective cover. Which became an obstacle during the installation of the video card. But on the other hand, Asus did not go beyond the size of the motherboard. But the EVGA did not take into account the fact that on the motherboard there may be some additional decorative or protective elements that can be located in zone 2 and 3 slots.
The only important point is if the stiffeners are located outside the body, then their length should be significantly less, otherwise these edges will conflict with the computer case.
Speaking seriously, given the increased weight of the air-cooling system at 2080T, it would be much more efficient to equip with branded supports that support the bottom of the video card.
 

My issue is with the case itself.

Contact the case manufacturer and/or buy a new computer case.

It’s not strictly a case issue. Part of the problem is the Maximus XI line of boards. They don’t all line up every well with the stand-off alignments in the case. I have a Phanteks Evolv X and I ran into a similar problem when I was building my rig almost a year ago now. In my case the motherboard IO would not sit completely flush to the IO at the rear of the case if the standoffs were 100% aligned. As such I had to screw in the mounting screws for the board at about 75% tight for at least 3 of the mounting holes. My IO is flush but the board itself is not lined up with the standoffs 100% because of this issue.

It seems like you are having a similar problem. Changing the case may not totally alleviate the problem.