See here: Cannot access files after upgrade to Nextcloud 25 - #10 by MichaIng
While formal removal of 32-bit support was intended (since no automated tests are done for 32-bit and there were always long standing issues regarding trashbin and >2 GiB file downloads), breaking files app and sync was not intended, but coincidentally merged with a sub module upstream change: Remove 4GB file size workaround for 32bit OS / Stream Videos on IOS by schoetju · Pull Request #184 · sabre-io/http · GitHub
Check here for a workaround, though no guarantee that it does not cause issues elsewhere, but it works fine on my instance: Cannot access files after upgrade to Nextcloud 25 - #6 by Kai21
Some guys are aware of the issue now, including the change in sabre/http and the devs of this module. Let’s see whether this can be fixed/reverted quickly, but likely not during the weekend 
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