Haven't tried to resolve the sleep issue because I never sleep;).
Basically I turn the sleep option off by running this command in terminal.
sudo pmset -a sleep 0;
Please let me know if you find a way.
From my exprience with Gigabyte x570 board, the F11 bios is the best bois so far. I use x570 pro wifi and I had the same issue on F20b with my 5500xt GPU. After switching to F11, I was able to enter the recovery mode and install catalina successfully.
Update from 10.15.5 today, works as usual.
CPU: Ryzen 3950x
GPU: Sapphire Radeon RX 5500XT 4GB
RAM: 32GB of Corsair LPX 3200MHz
Motherboard: Gigabyte Aorus Pro X570 Wifi (have to use bios F11. otherwise can not go into the recovery)
Audio: ALC1220VB (on Motherboard)
Ethernet: 1G (on...