Thank you very much for your help!
I tried different approaches; currently I am testing a solution that involves writing my own data_collator to pass to the Trainer instance:
def dummy_data_collector(features):
    batch = {}
    batch['input_ids'] = torch.stack([f[0] for f in features])
    batch['attention_mask'] = torch.stack([f[1] for f in features])
    batch['labels'] = torch.stack([f[2] for f in features])
    
    return batch

This seems to be working, but I will need to do some more testing