I would love to know how you found that one, so I can look one that supports 60 W (12 V 5A). If i search that model directly, i can find it on APC’s website, but no combination of search terms brings it up otherwise, not router ups, not laptop ups… All I’m getting are the standard ups models with 120 VAC outlets.

How would you wire the barrel style adapter directly to the battery, and charge it at the same time?

You can install nextcloud on any file system afaik. Mine is btrfs. But yes, I’ve had unrecoverable database corruption with power failure. It uses mariadb for the database.

Thank you that is a great insight and may be what I do if I can’t find an elegant DC solution.

How did you wire the battery up to the router, with the car battery maintainer attached?

I’m pretty sure that the UPS failed because the battery was 5 years old. The manual specifies needing to replace the battery every 3-5 years.

I double checked the router and the power supply (which is medium-big size) says 12V 5A, which comes out to 60 W

I can do this, just trying to optimize away some unnecessary power losses to get longer lifetime out of the batteries.