Recently my Ubuntu Desktop has been unable to wake after a suspend. Here is my current OS version and hardware information. Perhaps you are in the same situation. The following output is created using the inxi -F command.

System:    Kernel: 5.11.0-43-generic x86_64 bits: 64 Desktop: Gnome 3.36.9 
           Distro: Ubuntu 20.04.3 LTS (Focal Fossa) 
Machine:   Type: Desktop Mobo: ASUSTeK model: CROSSHAIR VI HERO v: Rev 1.xx
           UEFI: American Megatrends v: 7803 date: 06/17/2020 
CPU:       Topology: 8-Core model: AMD Ryzen 7 1700 bits: 64 type: MT MCP L2 cache: 4096 KiB 
           Speed: 1374 MHz min/max: 1550/3000 MHz Core speeds (MHz): 1: 1374 2: 1373 3: 1374 4: 1520 5: 1375 6: 1374 7: 1374 
           8: 1373 9: 1375 10: 1374 11: 1373 12: 1374 13: 1375 14: 1372 15: 1374 16: 1373 
Graphics:  Device-1: NVIDIA driver: nvidia v: 495.44 
           Display: x11 server: X.Org 1.20.13 driver: nvidia unloaded: fbdev,modesetting,nouveau,vesa 
           resolution: 2560x1440~60Hz 
           OpenGL: renderer: NVIDIA GeForce RTX 3060/PCIe/SSE2 v: 4.6.0 NVIDIA 495.44 
Audio:     Device-1: NVIDIA driver: snd_hda_intel 
           Device-2: Advanced Micro Devices [AMD] Family 17h HD Audio driver: snd_hda_intel 
           Device-3: C-Media type: USB driver: hid-generic,snd-usb-audio,usbhid 
           Sound Server: ALSA v: k5.11.0-43-generic

Apparently this issue occurs when you are using a nouveau driver like shown above. The fix I found was to edit /etc/defaults/grub and add nouveau.modeset=0 to the line that starts with GRUB_CMDLINE_LINUX=.

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX="nouveau.modeset=0"

Now run update-grub. The problem should now be fixed after a reboot.