I give it 3 and not 4 because the screen does not light up.
Simple digital thermostat with accuracy in room temperature.
It requires familiarization because you see the actual temperature and not the desired one on the screen. When the boiler turns on, a small flame appears and you hear the familiar click of the command.
You can change the desired temperature in both comfort and economy mode. So far, I have set it to 21 degrees during the day and 18 at night, and it seems to work perfectly.
When replacing it with the analog thermostat, caution is needed because you connect 2 wires and not all 3 that the old one has.
Connect the power (L) and the command and leave the neutral (N) out.

I don't give it 5 stars because I just bought it and I have a small basket. As a first impression, it seems to do its job.
It operates with 2 AAA batteries that are inserted from the side without having to remove the thermostat from its position to replace the batteries. The screen is NOT illuminated.

Find the operating instructions here:
https://hit.sbt.siemens.com/RWD/modules/kernel/UI/slow/GetBinData.aspx?DTP=Operating+Instructions&SID=A6V13156980&EXT=.pdf&VALUE=Assets%5cA6V13156980_de.pdf&KEY=3&RT=1671061534215

Find the installation instructions here:
https://hit.sbt.siemens.com/RWD/modules/kernel/UI/slow/GetBinData.aspx?DTP=Mounting+Instruction&SID=A6V13156953&EXT=.pdf&VALUE=Assets%5cA6V13156953_Mounting%2520instruction%2520RDD50.1_de.pdf&KEY=3&RT=1671061534214

Initially, I wanted to get the Siemens RDH100 but I avoided it because of the negative reviews it has and because many people wrote that the wheel was breaking, so I decided to get this one that has buttons +/- instead of a wheel.

It looks quite similar to the Siemens RDD100.1 but I preferred this one because it has a slightly more modern design and a nicer screen.

Finally, I should mention that I ended up with this one after being disappointed with a Smart Wifi thermostat from Hysen which worked great for the first 2 years until it burned out, so I decided to try something more reputable and simple in operation, thinking that it would prove to be more reliable in the long run.

If any issues arise, I will come back and update.