Which Chromebook model do you have? You might want to try using a USB headset or Bluetooth earbuds or possibly just some headphones while using the built in microphone. Sometimes on smaller devices the microphone will pickup the audio from the speakers and cause all sorts of feedback issues for everyone in the meeting.
I have a HP Chromebook x360 with 8GB of RAM…..I suspect that there are many moving parts to this challenge. The USB headset or headphones is a good idea. I did not think of that. I suspect that the bluetooth might draw from the resources (RAM) of the chromebook. Which would be your first choice? USB headset ? or headphones?
I am already using an ethernet to USB adapter which has helped some. Do you think that a ethernet to HDMI adapter would work better?