Repairing botched Debian installation

I am attempting to install Debian 10 on a HP 15 laptop. I've had versions of Ubuntu running on the laptop in the past, so I know that it is capable of running Linux. I have been using the AMD64 netinstall image on a USB thumb drive. During installation, I was told I needed the following firmware: rtlwifi/rtl8188efw.bin and rtl_nic/rtl18106e-1.fw . I didn't have the firmware handy at the time. My first five attempts with various display managers were able to install, but would not fully boot. The Debian Display Manager would hang on the Gnome display manager. Others would display the message "rt18188ee: Firmware is not ready to run". I was finally able to get a bootable installation with LXQt. Currently, the laptop boots into a shell, without xwindows. The first time I ran 'startx' I was given the error message "/root/.Xauthority does not exist". Now I get multiple error messages cumulating in "Unable to connect to X server: connection refused". During boot, the following message is displayed:amdgpu requires firmware installed.

I updated my /etc/apt/sources.lst with contrib and nonfree, hoping that would correct my problem. However, I have absolutely no network connectivity, either via Ethernet or wifi. When I am using Ethernet, I am given an IP address by my router, and my router shows that my laptop is connected. However, for some reason, my laptop is unable to connect to the internet. All of the other devices connected to my router are able to connect without any problems. I suspect that the problem could be due to the rtl_nic firmware issue. However, when I was running off of the netinstall image, I was able to connect via wifi.

I'm out of ideas on how to correct my installation. Any assistance would be appreciated.