How can I export contact groups?
This answer is based on beeshyams's comment.

Download &amp; install the SA Contacts Lite application; it is available on places where you don't need an account, e.g. via APKPure.com.
Start the app.
In Settings:
3.1 enable Export All Fields.
3.2 Disable Export Photos.
3.3 Enable Merge Duplicates.
Click Export, then Start.
A format selection dialog will come up. Enable Backup and disable everything else; press Next.
An account selection dialog will come up (= the account whose contacts you want to export). Typically you'll want to enable just the default account. Press Next.
Select the range of contacts to exprot - probably all of them, so just press Next.
Wait for the app while it's `preparing to export contacte
Select the destination for the export - typically just a file on the device's storage somewhere.
Patiently wait for the duplicate merge and actual export to occur. I have no idea why it takes so much time, given how there's so little data.
Choose a way to save the output file; &quot;SD Card&quot; is safe, but there are also options to send it to your Dropbox/Box/Google Drive account or to email you the file.
Ensure the output file is actually placed at/sent to your chosen location.

Then, you can import your group associations as described in discussed in this question.