The 3080 is more than enough power and is a frequent piece of hardware between users, so it’s anomalous that this is occurring consistently. 5 second delay on rendering is immense. Reinstallation may help if the issue isn’t RAM or VRAM, it could be corrupted drivers, though your driver reinstallations would have cleared that before. Windows 11 had a couple of issues earlier in it’s life with UE but I cannot speak for now.
This thread has many driver side tricks, but no idea if it will work out.