Apc smart ups 1500i (smt1500i) connection to my HA server

Hi there.
I have a APS Smart UPS 1500I (SMT1500I).
On my network i have a synology NAS and HA mini computer (Beelink MINI S12 Pro).
If I connect the USB port to my NAS it can gracefully shut down before UPS runs out of juice. What I would like to do is connect my UPS to my HA computer (Beelink MINI S12 Pro) and control everything from there (including shutting down my NAS).
If this is possible, how can I do it?
Thank you.

Thank you so much for your help.

Myself failed to add this model to NUT. Perhaps did smth wrong.

In my UPS settings I have enabled TCP Modbus. Since it is connected to a ethernet switch via snmp card ethernet port. However the NUT addon still cannot connect to the UPS. Here is the log.
What would you recommend?
Thank you.

s6-rc: info: service s6rc-oneshot-runner successfully started
s6-rc: info: service base-addon-banner: starting
-----------------------------------------------------------
 Add-on: Network UPS Tools
 Manage battery backup (UPS) devices
-----------------------------------------------------------
 Add-on version: 0.16.1
 You are running the latest version of this add-on.
 System: Home Assistant OS 16.3  (amd64 / generic-x86-64)
 Home Assistant Core: 2025.11.1
 Home Assistant Supervisor: 2025.11.1
-----------------------------------------------------------
 Please, share the above information when looking for help
 or support in, e.g., GitHub, forums or the Discord chat.
-----------------------------------------------------------
s6-rc: info: service base-addon-banner successfully started
s6-rc: info: service fix-attrs: starting
s6-rc: info: service base-addon-timezone: starting
s6-rc: info: service base-addon-log-level: starting
s6-rc: info: service fix-attrs successfully started
[20:27:58] INFO: Configuring timezone (Europe/Istanbul)...
s6-rc: info: service base-addon-log-level successfully started
s6-rc: info: service base-addon-timezone successfully started
s6-rc: info: service legacy-cont-init: starting
cont-init: info: running /etc/cont-init.d/nut.sh
[20:27:58] INFO: Setting mode to netclient...
cont-init: info: /etc/cont-init.d/nut.sh exited 0
cont-init: info: running /etc/cont-init.d/nutclient.sh
cont-init: info: /etc/cont-init.d/nutclient.sh exited 0
s6-rc: info: service legacy-cont-init successfully started
s6-rc: info: service legacy-services: starting
services-up: info: copying legacy longrun upsd (no readiness notification)
services-up: info: copying legacy longrun upsmon (no readiness notification)
[20:27:58] INFO: Starting the UPS monitor and shutdown controller...
   0.000000	fopen /run/nut/upsmon.pid: No such file or directory
   0.000008	Could not find PID file to see if previous upsmon instance is already running!
   0.000119	Using power down flag file /etc/killpower
   0.000188	UPS: [email protected] (secondary) (power value 1)
   0.000203	[D1] debug level is '1'
   0.000223	Warning: running as one big root process by request (upsmon -p)
   0.000327	[D1] Saving PID 266 into /run/nut/upsmon.pid
Init SSL without certificate database
   0.001681	upsnotify: notify about state 2 with libsystemd: was requested, but not running as a service unit now, will not spam more about it
   0.001688	upsnotify: failed to notify about state 2: no notification tech defined, will not spam more about it
   0.001689	upsnotify: logged the systemd watchdog situation once, will not spam more about it
   0.001691	[D1] Trying to connect to UPS [[email protected]]
   0.004148	UPS [[email protected]]: connect failed: Connection failure: Connection refused
{"message":"Event nut.ups_event fired."}Network UPS Tools upsmon 2.8.1
s6-rc: info: service legacy-services successfully started
   5.004572	[D1] Trying to connect to UPS [[email protected]]
   5.007457	UPS [[email protected]]: connect failed: Connection failure: Connection refused
{"message":"Event nut.ups_event fired."}Network UPS Tools upsmon 2.8.1
  10.008215	[D1] Trying to connect to UPS [[email protected]]
  10.011098	UPS [[email protected]]: connect failed: Connection failure: Connection refused
  15.011256	[D1] Trying to connect to UPS [[email protected]]
  15.013997	UPS [[email protected]]: connect failed: Connection failure: Connection refused
  20.014201	[D1] Trying to connect to UPS [[email protected]]
  20.017225	UPS [[email protected]]: connect failed: Connection failure: Connection refused
s6-rc: info: service legacy-services: stopping
  20.404601	Signal 15: exiting
Network UPS Tools upsmon 2.8.1
[20:28:18] INFO: upsd stopped, restarting...
[20:28:18] INFO: upsmon stopped, restarting...
s6-rc: info: service legacy-services successfully stopped
s6-rc: info: service legacy-cont-init: stopping
s6-rc: info: service legacy-cont-init successfully stopped
s6-rc: info: service fix-attrs: stopping
s6-rc: info: service base-addon-timezone: stopping
s6-rc: info: service base-addon-log-level: stopping
s6-rc: info: service fix-attrs successfully stopped
s6-rc: info: service base-addon-timezone successfully stopped
s6-rc: info: service base-addon-log-level successfully stopped
s6-rc: info: service base-addon-banner: stopping
s6-rc: info: service base-addon-banner successfully stopped
s6-rc: info: service s6rc-oneshot-runner: stopping
s6-rc: info: service s6rc-oneshot-runner successfully stopped