We need a way to easily maintain the country list. The list is currently based on ISO 3166-1 I believe, but isn't perfectly up to date.
https://github.com/ibexa/core/blob/main/src/lib/Resources/settings/fieldtypes.yml
As an yml config file it is easy to edit, but we have to ensure updates won't break edits.

Why? Because no country list is neutral. We need a documented way for clients to adapt this list to their needs. Even the UN / ISO 3166 source includes controversial items like "Taiwan, province of China", "State of Palestine", Falklands/Malvinas, Western Sahara, and more.
https://en.wikipedia.org/wiki/ISO_3166-1#Naming_and_disputes

...yet ISO 3166 doesn't include Kosovo, which has passed the criteria for inclusion but isn't yet actually included. It's widely recognised as a country especially in Europe and the West which is our main customer base, but not in Serbia and some other countries. It is currently included in our list after a customer requested it in EZP-32302, and it might be controversial to remove it. Customers should be informed about these issues and be given a way to make their adaptations.

This repo https://github.com/lukes/ISO-3166-Countries-with-Regional-Codes/blob/master/all/all.csv
strictly follows ISO-3166. We could use that, with or without our own changes, and document the best way to modify it. We should also establish a routine for regularly updating our country list.

Summary

1. Establish a routine for maintaining the country list, if possible with automation
2. Decide if our default list should be ISO 3166 which means removing Kosovo
   or if our default list should include some modifications, like Kosovo
3. Document the recommended way to modify the country list