I also agree that sync with LR Classic is the best option, however there are ways to export the DNGs, and you can use this option to backup your images in case they get deleted when changing to a different Adobe account.
In the LR mobile app, go to the desired folder and select the images you'd like to export, (clicking on the three dots on the upper right corner - > select). You can even select "All photos" by clicking on the check box on top left.
After you have selected the photos, select "Share" and then "Export as", and there select "Original". From there you can export them to the "Files" app, or to a shared folder such as google drive. In theory you can also use dropbox, but i only get to export one image at a time with this option.
If you change the Adobe account and it does not keep any previous image, you can reimport them from the location you choose before.