I bought the Tescom Leo Plus 510W and I'm using it for the first day with the following setup:
• It is connected directly to the wall socket.
• On the first UPS output I have a power strip with a switch (red light) where I power: computer, monitor, 5.1 speakers, Google Home, router, 43" TV, soundbar, Xiaomi lamp, Ethernet splitter, and Inkjet printer (NOT laser).
• On the second output I have only my Synology NAS, for full protection and safe shutdown in case of power outage.
What I tested:
I did a small 2-minute test by disconnecting the UPS from the socket to see if it holds the devices.
• Turned on: PC, monitor, speakers playing music, Google Home, router.
• Everything else was on standby.
• The UPS worked normally, without any problem.
• I did not try to fully drain the battery to see the maximum autonomy, it was just a small functionality test.
What I liked:
• Works like clockwork, with stable voltage and correct load indication.
• Silent and without odors, as some others mention.
• The ability to connect a power strip to the UPS is practical and safe, as long as you do not exceed 50% of the maximum load.
• The automatic voltage regulation (AVR) keeps the power stable and protects the devices.
Conclusion:
The Tescom Leo Plus LCD 510W seems reliable and practical, protects against surges and power outages, and my small test showed that it works properly even with several devices on at the same time. However, it is the first day I use it and its real reliability will be seen in the future.
Rating: 5/5 ⭐ – safe, practical and silent.

I use it for the router, modem, raspberry pi, and zigbee gateway (for home assistant). The load does not exceed 3%, with the need to be for the above. I definitely want 1 hour of endurance for this, so I chose these specific specs.

I have utilized it to the fullest (and USB for communication with the RPi via upsnut) and for protection in case of overvoltage in the DSL wiring.

It makes some beeping at first but then stops. With the USB connection, I have the option to mute the beep more quickly.

Its disadvantage is that it still smells even when in online mode, which is a bit annoying especially after 1 month. Of course, I have it in a hallway, but it is regularly ventilated. That's why -1 star.

Anyone who wants to do monitoring on Linux, this is the configuration for NUT:

[tescom_ups]
driver="nutdrv_qx"
subdriver="hunnox"
desc="Tescom Leo Plus LCD 850A"
port="auto"
vendorid="0001"
productid="0000"
protocol="hunnox"
langid_fix=0x0409
novendor
norating
noscanlangid

I have successfully connected it to home assistant

Very respectable, very honest, and so far it has proven to be a champ during all the consecutive power outages we've had due to bad weather and DEH's work, a situation that I would say is permanent for us. It functioned protectively during outages when the power would return for a few seconds, drop again, and then come back. It didn't notice anything and protected the PC without the slightest problem, while also giving the necessary time to complete your tasks and shut down if you were on the computer at that moment, or simply to have peace of mind during the consecutive outages that you wouldn't find your belongings toasted. It always has an audible alert so you know exactly what is happening. I also really like its design; it's an aesthetically pleasing and beautiful product to see on your desk. There was indeed a strange smell specifically when it was called to function during the power outages, what friends here say in the comments is true. I don't know exactly what it is, but I didn't notice anything else strange happening. If any friend has an answer to this, please write it here. The screen is also very good; even if you are a beginner in these things, you understand what you need to do and what it shows. You just plug it in, connect the computer and the screen, and let it do its job. Now I will get two more. Worth it.