drivers - Ubuntu Freezing after login, can't install gdm3, other solutions not working

I am on Ubuntu 18.04.3 LTS, and the computer freezes after I enter in my login information.

I have looked thoroughly at the solutions presented on Ubuntu gets stuck in a login loop but none of them work for me. I changed the ownership on ~/.ICEauthority and I don't have a ~/.Xauthority

I am using gdm3, not lightdm. I switched to lightdm, but then uninstalled it.

Now I cannot install gdm. Package 'gdm' has no installation candidate. What?! I've also tried gdm3 which doesn't appear to exist either. Solution here How do I switch from LightDM to GDM? doesn't work

per Freeze after login Ubuntu 18.04 I tried sudo add-apt-repository ppa:graphics-drivers/ppa I get errors that this bionic Release does not have a Release file.

as suggested on other pages, I've done sudo ubuntu-drivers devices which outputs

==sys/devices/pci0000:00/0000:00:14.0/usb1/1-7/1-7:1.1 ==
modalias: usb:.......
vender: Realtek Semiconductor Corp.
driver : rt18812au-dkms - distro free

the output of apt-search gdm3 is that I have gdm3/bionic-updates,bioinc-secuirty, now 3.28.3-0ubuntu18.04.4 amd64 [installed] GNOME Display Manager

output of sudo apt-get check shows no problems.

output of sudo lshw -C memory:

*- firmware
 description: BIOS
 vendor: LENOVO
 physical id: 0
 version: 3JCN19WW
 date: 08/10/2016
 size: 128 KiB
 capacity: 6016KiB

 capabilities: pci upgrade shadowing cdboot bootselect edd int13floppynec int13floppytoshiba int13floppy360 int13flopppy1200 int13floppy720 int13floppy2880 int9keyboard int10video acpi usb biosbootspecification uefi
 *-cache: 0
 description: L1 cache
 physical id: 5
 slot: L1 cache
 size: 128KiB
 capacity: 128KiB
 capabilities: synchronous internal write-back unified
 configuration: level=1
*-cache: 1

 description: L2 cache
 physical id: 5
 slot: L1 cache
 size: 512KiB
 capacity: 512KiB
 capabilities: synchronous internal write-back unified
 configuration: level=2
*-memory
 description: System Memory
 physical id: 24

 slot: System board or motherboard
 size: 8GiB
 *-bank:0
  description: SODIMM DDR4 Synchronous 2133 MHz (0.5ns)
  product: M471A5244BB0-CPB
  vendor: Samsung
  physical id: 0
  serial: 00000000
  slot: ChannelA-DIMMO
  size: 4GiB

  width: 64 bits
  clock: 2133MHz (0.5ns)
 *-bank:1
  description: SODIMM DDR4 Synchronous 2133 MHz (0.5ns)
  product: M471A5143EB1-CRC
  vendor: Samsung
  physical id: 1
  serial: 974F4E14
  slot: ChannelB-DIMMO
  size: 4GiB

  width: 64 bits
  clock: 2133MHz (0.5ns)
*-memory UNCLAIMED
 description: Memory controller
 product: Sunrise Point-LP PMC
 vendor: Intel Corporation
 physical id: 1f.2
 bus info: pci@0000:00:1f.2
 version: 21
 width: 32 bits

 clock: 33MHz (30.3ns)
 capabilities: bus_master
 configuration: latency = 0
 resources: memory:bi224000-bi227fff

output of free -h

        total   used   free   shared   buff/cache   available
Mem:     7.7G   355M   6.8G      106M       574M      7.0G

Swap:    7.9G     0B   7.9G

now I'm totally stuck. How do I get my Ubuntu back?