DSL or video doorbell with telecommunications cable A2YL2Y 6X2X0,6 TR?

I just see that 2-wire doorbell systems could also be an option, since power is available at the gate. However, the wire comes out in the HAR. Is there a portable screen variant of the 2-wire doorbell systems?

Something like that could be built with a Gira TKS. Two-wire video door intercom outside, TKS + TKS-IP-Gateway inside, end device (e.g. tablet or smartphone) inside via WLAN. Note: very expensive. Whether there are any cheap solutions, I don't know. Staying completely on IP will be cheaper in the end.

The 2-wire to Ethernet converters are exactly the right thing, but unfortunately also much more expensive in terms of price (even renkforce at Conrad 170 EUR for 2 end pieces) than either switching directly to a 2-wire system or simply laying another Ethernet cable.

In my opinion, two-wire is anyway nothing more than an emergency solution.

I inquired in the electrician forum and also consulted with local electricians, the cable is sufficient for an intercom system with audio, video, and door opener. I will separately lay a Cat7 installation cable as an option for another video system (POE with connection to smart home or similar). Telekom demands their 800 EUR flat rate anyway, so they can also dig and lay cables themselves.

I am quite sure that you won’t get far with the calculated flat rate of 800€. As already partially noted, that is only a flat rate for a connection of about 10-15 meters. (I don’t have the exact data in my head and I am not at home to check.) As soon as you exceed the standard distance, every meter costs extra. I was affected by this myself...
Back then, I dug a trench myself, in which the city’s fresh water pipe, Telekom’s telephone cable, and the power cable just had to be laid.
In the end, I had to coordinate the staff from the waterworks and a civil engineering company commissioned by the city so that the lines could be laid almost simultaneously.
I laid an empty conduit for myself as well, which I can use if needed...
If you have any more questions, feel free to write to me. I hope I could be of some help to you.

Currently, I have the feedback that Telekom or the subcontractor is laying the line up to the house – including the 30-40m – but not into the empty conduit.

Currently, there is a dispute anyway because we have the empty conduit up to just before the house, but not into the HAR. This is supposed to be done by us – but we would have to rent a mini excavator again, etc.

Now the planner wants to state that digging has to be done and we should clarify this with the responsible civil engineer via a short communication channel.