Based on my understanding the current SPList connector is only for SP online and not for sharepoint hosted on On Prem.
So you would anyhow have to write your own custom logic to extract data from on Prem SPlists.
Also Service principals are present in your Entra ID (cloud AD) and since your SPlist is hosted on On-Prem, the Service principals cannot be reveres synced into on Prem AD hence you cannot grant SP access on On-Prem SP