I always had difficulties with Mandragora seeds.
I read somewhere that they germinate easy in a refrigerator. And they did.
Species is probably Mandragora autumnalis from seeds I collected in Krete some years ago.I kept the seeds with some life sphagnum in a sealed plastic bag.
3 weeks later they germinated and I put them including the moss in a pot where Tomatoes were the year before.
Substrate was just from a public Compost place without any mineral additives. Just rotten plant stuff, wood and some cow dung (It is run by a cow farmer)
Now they started their third grow cycle and one is already flowering size.
I did not use GA3.
Some tomato fertilizer one or two times this year and of course some Boron in homeopathic doses was all they got apart from water.