Payment completed, order in draft. Twint

Can confirm, we are having the same issue on our website as well.

@cmd87 I think I have found the culprit.
It's necessary to add in your payment in Drupal the Webhook Sign Key (sign2). Also you need to get this key from Datatrans
In
UPP Administration
Security
Security signature
Copy "important parameters will be digitally ..."

And also specify the URL in
UPP Administration
UPP Data
URL Post

According to Drupal
Required when using webhooks. Note that the webhook (URL POST) must be configured in the Datatrans Backend and only a single, static URL is supported per merchant. Webhook URL: /commerce/datatrans/notify.

This should make it work. Basically when the order is paid in Datatrans, a webhook will be sent to commerce/datatrans/notify and the order will be updated in drupal.

I am still not sure if using the option "An additional Merchant-IDentification will be send with payment messages" in Datatrans will work instead of using "Important parameters will be digitally signed (HMAC-SHA256) and sent with payment messages"