Hi,
you need to configure IP under physical interface/subinterface (e.g Gigabitethernet1)
Create tunnel interface (interface tunnel1) with ip unnumbered Gigabitethernet1, tunnel source physical interface Gigabitethernet1, tunnel mode sdwan.
Then go to sdwan mode and just enable "tunnel-interface" under physical interface (e.g Gigabitethernet1)
https://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/SDWAN/sdwan-wan-edge-onboarding-deploy-guide-2020nov.pdf
HTH,
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