Dear @John_Painter
Thanks for sharing this important topic, and indeed many countries are using versions behind.
To my findings the barriers to upgrade are not major even when countries have experts and resources to retrain its a challenges.
One major challenge has been having a test/training server where all the testing and training can happen before upgrade. They need to test extensively before they can can upgrade production to eliminate fears. Training is not a major barrier, because its easy for the users carry on with the new versions.
Also if there are custom Apps running on the old versions, its been difficult to get the developers of those Apps to upgrade them, because of the API changes after 2.28.
Regards