This solution allows you to use the Play Store and other providers (such as F-Droid) to install packages which are not in Play Store. The only downside to this way of doing things is that you will not be notified of updates. You will need to manually look for updates and perform manual updates.
This is all taken from https://www.malachisoord.com/2020/07/20/sideloading-android-apps-on-chromeos/, which explains it all so I won't replicate it. If you're familiar with ChromeOS, the summary is below
sudo apt update && sudo apt install adb
sudo adb install my-apk.apk