I just went through this process to upgrade from LTS (5.6) to 5.14 and wanted to share my experience.
One gotcha I ran into is that 5.10.24 supports device firmware 4.0.9 or later only. My APs (a mix of AP-AC-LR and AP-AC-Pro) were all on firmware 3.9.xxx. After upgrading the container to 5.10, the controller was unable to show any information about these APs. Even worse, 5.10 is unable to upgrade 3.9 devices, and it migrates the Unifi database in appdata to a new format. So you can't update the firmware or roll back easily to 5.6.
I could have updated the firmware on my AP's by SSH into each AP, but I didn't want to risk running into any more gotchas and problems from Ubiquity. I had made a backup of my appdata before moving to 5.10 and I restored it. It is the first time I have ever needed to restore the appdata in many years of running unRAID, but I am very appreciative of the developers of Community Applications Backup / Restore Appdata plugin. After restoring the original appdata, I changed the container back to 5.6 and used the 5.6 controller to upgrde the device firmware on the APs.
I was not sure what firmware version was best to move to on the APs. I went with 4.0.80 based on several comments in Ubiquity forums, but many also seem to like 4.3.20. Might need to revisit this again.
Once the firmware was updated, the migration to 5.10 and then to 5.14 went smoothly, and the APs appear to be working well.