I somehow missed the thread. If Telekom offers Entertain, it usually works without any issues. Even if it is only offered with DSL 16,000. However, it is correct that only a maximum of 2 SD streams or 1 HD stream can be watched/recorded simultaneously.
DSL 16,000 unfortunately does not always mean that 16,000 actually arrive. However, if Entertain is offered, it is ensured that 10,000 arrive, which is sufficient for IPTV. But if it is clear from the start that only 2000 or 6000 arrive, Entertain will not be offered at all.
Furthermore, there is also Entertain via SAT. As the name already suggests, the TV portion then comes via SAT and a satellite dish + appropriate cabling is required.