Have you tried following the relevant course sections 8? (I linked to translation but summarization should be the same as well).
Basically you are supplying raw datasets to the Seq2SeqTrainer and this can’t work, as it will need the inputs to the models (input_ids, labels, attention_mask etc.) so you need to tokenize your inputs and labels. This is all done in the examples you mention once you have your dataset with one column for the input texts and one column for the target texts.