Sorry to say but how you are framing things is simply not true anymore.

You are not required to buy their "Glasfaser Modem 2" you can buy any ONT Modem.

You are not required to use any of their equipment, they give you the data to connect via PPPOE directly.

I bought a house with FTTH in 2023 and never used any Telekom hardware. Nobody forces you to use the peer DNS. The telekom DNS isn't complying to https://cuii.info/anordnungen/ because they want to but to avoid being sued everytime some company wants to block an illegal streaming site.