nut VS DietPi

> what software do you recommend for gnu/linux to take input from the UPS to tell the laptop to shutdown?

https://networkupstools.org/

The Synology software is based on N.U.T. https://networkupstools.org and the Plus 1100 (listed on NUT as the Easy Power 1200) is supported in the native package with the 'blazer' driver. If you have the skills, I would SSH into the NAS and see if the device is 'noticed' or better yet recognised by the USB sub-system when you plug it it. (Normal Linux would use the lsusb command to see devices but I have no NAS handy to see if this is valid on the Synology)

Others have answered the hardware part of your question. I have not seen much mention about the software to control graceful shutdowns. For this I suggest you look at the ”Network UPS Tool” (NUT for short) project (https://networkupstools.org/). It is mostly manufacturer agnostic with clients for a vast array of hardware components.

You're looking for NUT.

Network UPS Tools is one option: https://networkupstools.org/

APC is giving me pre-nut clarity.

So no, the NAS does not monitor the battery level. The UPS does that. The NAS just acts on the messages it receives from the UPS via Synology's version of NUT - Network UPS Tools (https://networkupstools.org/). The NAS will first receive the ON_BATTERY/POWERFAIL signal. Then, eventually the BATTERY_LOW signal at which time the UPS will shutdown. So you really need to set a time for it to shut down *BEFORE* you get BATTERY_LOW.

DietPi is a lightweight Debian based Linux distribution for SBCs and server systems, with the option to install desktop environments, too. It ships as minimal image but allows to install complete and ready-to-use software stacks with a set of console based shell dialogs and scripts.

The source code is hosted on GitHub: https://github.com/MichaIng/DietPi

That's a good point, but the array of devices supported by the DietPi team is extensive: https://dietpi.com/

Before someone starts the usual yadda yadda about the RPi biger community, the OS not having long time support etc. I would repeat one more time: do not rely on board vendor supplied images; this is valid for pretty much all boards. Just go to Armbian or DietPi pages and you'll almost certainly find one or more images that work on your board and forums to discuss about them with very knowledgeable people.

https://www.armbian.com/download/

https://dietpi.com/#download

Those projects are well worth a contribution, as they don't have a giant like Broadcom behind them.

> bananapi do a lot of boards but their software story has been a bit poor

This is quite common with other board manufacturers too. I'd rather suggest to ignore completely their cobbled together distros, often also tainted by proprietary modifications, that become unmaintained in a few years, and see if they're among the many supported by Armbian or DietPi.

https://www.armbian.com/download/

https://dietpi.com/#download

The full release notes can be found at: https://dietpi.com/docs/releases/v8_25/

RPi OS = diet pi https://dietpi.com/ - initial config via text file - SDcard burning out partially mitigated as writes log files to ram then flushes to SDcard reducing write cycles

You could also try very minimalistic distros like TwisterUI or DietPi which are most known for their use in the RasprebbyPi / SBC computers but which also have editions for desktop / laptop.