Question about TechniSat Digitradio 143 V3

conditionally yes. Either one with a built-in phono preamp or one with an interconnected phono preamp (available for 20.-). It is then connected to the AUX input (3.5mm stereo jack).

Ah something else 3.5 mm jack is a headphone output, sorry

Good day, without a phono preamplifier, if it is not already integrated in the turntable, it does not work, but apart from 3.5 mm jack aux, there are also 2 chinch inputs on this unit.

No, not to my knowledge. I take Digitradio into the amplifier via the tuner input and the record player via the phono input.

I have not looked
The unit is not at my house so I can't clarify it.
There are adapters with which you can connect record players to normal inputs.