Ignite Gallery version 4.9 and below do not work in Joomla 5.
Version 5 of Ignite Gallery was released on the 31st of October 2023. Version 5 of Ignite Gallery works in Joomla 5, and in Joomla 4.
Ignite Gallery version 5 will appear as an update in the Joomla Updater.
You can also download Ignite Gallery version 5 from the downloads page, and upload/install through the Joomla installer.
To upgrade from Joomla 4 to Joomla 5, please update Ignite Gallery to version 5, no extra steps are required.