Apple iPad mini storage is full or the device cannot install updates

The checks in more detail

Photos come next, and iCloud Photos with Optimize iPad Storage keeps full-resolution originals in iCloud. Games are large, and the Games folder in iPad Storage shows them. System Data can be a lot, and a restart and update trim it. Offloading an app keeps its data, and deleting a downloaded show removes only the offline copy. Keep a few gigabytes free, because updates and the camera need room. A USB-C external drive works with the mini through Files, so large videos can live on it.

Apple's Optimize iPad Storage setting also applies to Music, where Optimize Storage in Settings, Music removes songs you have not played for a while when space is low, and to Mail, where downloaded attachments are removed from the device when space is needed. If you read a lot of comics or PDFs, store them in iCloud Drive and open them on demand rather than keeping every file offline. Check the Documents and Data figure of apps like Books and Podcasts, since they keep downloads you have long finished with.

Photos that are shared in group chats are saved in Messages as attachments and take space even if you never saved them to Photos; use the Messages large attachment review to clear them. Cleaning these on a 64 GB mini can free several gigabytes at once. If you read digital magazines or comics, check each reader app's own storage settings, since many keep a cache of pages you have read that can reach several gigabytes, and a Clear Cache option in the app's settings reclaims it without removing your library. The same applies to podcast and audiobook apps, which keep downloaded episodes until you delete them, so set them to remove played episodes automatically.