The purpose of purchasing the router was to combine a problematic 100Mbps VDSL connection with a 5G mobile connection in order for the latter to function as a backup for the former and to accelerate both the upload (more important) and download (pleasant side effect) of large files from university servers. However, not all internet traffic of the house should pass through the 5G connection...
This specific device is perfect for "amateur" use and especially for the aforementioned scenario because: it is very affordable, has a small size, more than covers household needs, and is relatively easy to configure. Of course, if you struggle with the routers provided by telecommunications companies, you will definitely need help with this one. However, those of you who have some experience with networks will not have much difficulty. The manual is helpful and there are also some guides on YouTube.
I haven't worked with the router enough to write an objective and detailed review. I will do it when I have the relevant experience. What I want to do is give a hint to everyone who wants to combine 2-3 internet connections (wired or mobile) to power an internal network (home or small business): This specific router will do the job! Just remember, the key to achieving balancing is not the "Transmission → LoadBalancing → Basic Settings" menu (you will need that too), but the "Transmission → Routing → Policy Routing" menu.
Allow me, also, to inform those who do not know that if, for example, a 100Mbps connection is combined with a 50Mbps connection, we cannot download a file at a speed of 150Mbps. The two lines are not combined for downloading the same file. This is not a problem with this specific router, it is generally not feasible.

I use it in a small office with about 10 computers. We are IT specialists, so the installation did not bother us. The purpose was to utilize an INALAN optical (250/250) and a Cosmote VDSL (10/100) primarily for failover and secondarily for load balancing.
We discovered that load balancing also offers failover (as expected, but not explicitly mentioned anywhere).
Load balancing means that it will send each PC to a different line (with adjustable priority), it will not give one PC the full combined bandwidth of the two lines.
From our measurements, the interference in front of each Internet Access Router did not seem to impose a cost, with CPU utilization not exceeding 20%-40%.
The time it takes to realize that one line has dropped and transfer all the loads to the other is about 1 minute with any method we tried, so we left it on automatic.
For the average user who wants to utilize two lines, it is easy to install.
For anyone who wants more features, some reading will be required, as it is not a typical Internet Access Router.
Overall, I am very satisfied with my purchase.
NOTE 1: It accepts a USB stick as a 4G/5G modem, which I find very useful, although we have not tested it.
NOTE 2: Port Forwarding can be found in the Virtual Servers menu!!