I expected it (much) better. Unfortunately, I didn't research it, I relied on reviews and the "name."

Starting with the negatives:
1. If the cameras are on another network/subnet (where there is communication, no firewall, etc.), they just don't work properly. Or if they do work, for some reason they don't record. The live view works.
2. The tapo cameras work with onvif. It doesn't see them as tplink, and if you set them as rtsp, they still don't work/record properly. Thus, they lose various features (2-way audio, LED light, etc.).
3. Anyone who has dealt a bit with zoneminder or a synology surveillance station will be greatly disappointed. The web interface is terrible and poor, with very little customization. The PC application is slightly better, and the mobile app (though with even more limited settings) is a bit more user-friendly.
4. Sound does not pass through in live view. However, it is recorded.
5. You can't export events from the web interface. It's more difficult from the PC but possible. It's somewhat better from the mobile.
6. Sensitivity in motion detection is almost impossible to adjust. I didn't notice any difference in any setting.
7. Human detection or whatever else the tapo cameras do is not recognized by the NVR. Its own detections don't work with onvif/rtsp. They probably work with vigi, but I don't have any to test.
8. Live view from Firefox DOES NOT work. It works from Chrome (but not always, even though I've already loaded the certificate on the PC, it sometimes asks for confirmation).
9. Generally, many of the features (most probably) don't work. They probably need vigi cameras.
10. Oh, with HDMI, when I tested it on a 4K monitor, the two cameras I was viewing were on the 640x480 stream, resulting in a terrible image. I don't know if it changes, I didn't look into it much.
11. Finally, it doesn't support, at least with tapo, two-way audio.

Positives:
1. It is silent. It doesn't have a fan; I put in a 5200rpm disk, and it's fine. Just make sure to disable the buzzer (fortunately, you can customize this quite a bit).
2. You can also view it from the cloud if you enable it. Useful feature.
3. The quality doesn't drop significantly; I didn't notice anything in tests with two tapo 2K cameras.
4. If you set it to record 24/7, it will probably perform well.
5. It has HDMI, and you can connect it to a monitor and operate it with the (included in the package) mouse. Useful for some, I guess (I just tested that it works, I'm not interested, I put it in a corner and left it there).
6. The package also includes screws for the hard drive, etc. It only takes 3.5" by default (though I don't think there's any reason for a smaller size, it doesn't change anything).
7. It is very light. Essentially, inside it just has a small all-in-one board where the disk connects directly.

What I would like:
1. Support for cameras from other companies (well, I'm not even discussing TPLink). Not having to search for ports, etc. (though for rtsp/onvif, it's pretty much default).
2. To be able to send logs to a syslog server. It rebooted, and I don't know why.
3. Better sensitivity adjustment in recordings (motion detection).
4. Two-way audio!

Would I buy it again?
Nah, not even as a joke...

It connected relatively easily and 4 cameras were attached to it. Settings via mouse and silent. The cameras that were connected were 2 Tapo C320ws and 2 Tapo C210. Very satisfied. Through the app, there is the possibility of remote monitoring via mobile. It comes without a hard drive (like most recorders), so count on an extra 40-50 euros for a hard drive. IT SUPPORTS 3.5 INCH hard drives and not 2.5 inch, the screw bases require a 3.5 inch hard drive to fit properly. I chose a WD disk, the model HDD WESTERN DIGITAL WD23PURZ PURPLE SURVEILLANCE 2TB 3.5" SATA3. Works perfectly and silently. Supports hard drives up to 10TB and is eight-channel, which means up to 8 cameras can be connected to it.
UPDATE: Another recorder was purchased for another space with the installation of 4 new cameras. Very easy to use, many settings in its menu even for the most demanding customer. The only thing I would like is a Greek menu (for those who do not know English). Maybe this will be solved with a firmware upgrade.
USEFUL TIP: Tp Link recommends WD Purple 24/7 hard drives for its recorders. They have the ability to record 24/7 seamlessly without generating heat or noise

I bought it for a small NVR system with 4 TP-Link cameras. I would say it is a decent to good product. It is relatively small in size, although it could be much smaller if instead of being designed to accommodate a 3.5'' HDD, it was for a 2.5'' SSD. I installed a Samsung 870 Evo 512 GB and it recognized it immediately, as well as the TP-Link cameras. However, the installation of the SSD was not easy because it had holes for screws only for 3.5'' HDD and without including an adapter. Fortunately, one of the holes matched, but I consider it unacceptable not to have support for 2.5''. I haven't tried other cameras, so I don't know if they work, but based on the specifications, I don't think there will be a problem. This particular model, as well as the larger 16-channel one, does not support PoE. However, TP-Link has released models (obviously more expensive) with an integrated 8-port PoE switch. The software is also average, clearly much inferior to the one provided by TP-Link in the cloud, perhaps intentionally to make you pay subscriptions, as it does not support any of the advanced features like person recognition, intrusion recognition, and line cross recognition. It only supports motion detection, which is also very sensitive without significant sensitivity adjustment. Another thing it lacks is good disk space management. You either use the whole disk or none at all. This is not a problem for HDD, but for SSD it would be good to have the option to use a little less, which would help prolong the disk's lifespan. Another problem is that the management through the Vigi app contradicts the Tapo app. The settings of the latter override the settings of the former, to the point where it may not work. Although its performance is very stable and with low power consumption, I believe TP-Link still has a lot of work to do to improve this product. However, its price is very good, which improves things a bit.