Well, I've tried almost everything... Got a complete 2-layer sound deadening of the wheel arches, boot, front floor, 4 doors, tailgate and bonnet. Got soft, studless winter tyres that rate the quietest on the market. Replaced summer Falken tyres with the softest and quietest tyres as well. The car is quieter than before, but still very loud on any road that's less than perfect.
The last thing I might try is adding door seals as described by @parkerbol in another thread. But, to be honest, I've lost hope. I believe Corolla is the noisiest car I've driven (I've driven Honda Jazz, Honda CR-V, Mazda CX-30, Opel Grandland X, Toyota Camry, VW Passat, Hyundai Ioniq Hybrid, Skoda Octavia, Kia e-Niro, Kia Ceed). Maaaaybe Kia Ceed estate was as noisy as Corolla.
This is my only complaint about the car though. But hell, it's pretty uncomfortable and headache inducing. I have a 60km highway work commute every day, and I'm definitely not looking forward to sitting in an airplane for half an hour each evening after work... 😞