Hi @mathijs-fish,I completely understand your hesitation and appreciate your approach to seeking guidance!

I see you are trying to access the external files from dbfs mount location.
As you can see in the snapshots which you have shared, The reason behind the below error while trying to access the external dbfs mount file using "with open" is that you are using a shared access mode cluster.

@FileNotFoundError: [Errno 2] No such file or directory: '/dbfs/mnt/art/inbound.
Ltest/EUT_Alignment_20230630_20230712130221.csv'

This is a known limitation for Shared Clusters, where /dbfs path is not accessible. You can try using a single-user cluster instead to access /dbfs which supports UC.

Please refer:
https://docs.databricks.com/clusters/configure.html#shared-access-mode-limitations
https://docs.databricks.com/en/dbfs/unity-catalog.html#how-does-dbfs-work-in-shared-access-mode

And we also have a preview feature 'Improved Shared Clusters' that addresses some of the limitations of Shared Clusters.

Leave a like if this helps, followups are appreciated.

Kudos,

Ayushi