Lower limit screw for derailleur adjustment is already at its outer limit

I assume you mean that it is rubbing on the inside, and that you want the FD to be closer to the bike. In this case it might be that you have cable tension causing problems. You should adjust the L screw without cable tension. You can simply loosen the cable bolt to help with this, so that only the L screw is adjusting the start position, not the cable

If there is still rubbing with no cable tension whatsoever, then it might be your FD is not straight (it needs to be rotated).

Review https://www.parktool.com/blog/repair-help/front-derailleur-adjustment

for steps.

Possibly also if your FD is not the original one you might have chainline issues, but you have not said here what bike you have and whether GRX810 is the original equipment or your replacement - GRX810 FD chainline is 2.5mm outboard compared to a standard road FD (the crank is outboard by 3.4mm).