Earlier in April, Instagram announced that they are testing new fonts for stories with a limited pull of users. On August 3rd, these fonts became available to everyone.
It is not the first time when Instagram is sharing their development plans openly but it is still a quite rare case.
In order to try these fonts yourself, you need to get to the story editing screen and add some text. By default, you will see a slider for font selection at the bottom. There you will be able to see 9 different font options for you to choose from. It will also remember your font selection and it will be used as default when you will try to add text next time.
It is also interesting that there was a lot of different 3rd party tools which allowed you to customize text fonts for Instagram and now they made it a feature.
Did you try these fonts already?