Thanks Mike9241.
Well that does not make sense at all on Turbotax's behalf, especially seeing one can e-file amended returns for the several past years. And Turbotax allow to e-file amended State returns.
Edit: Turbotax clearly states in this support document e-filing is not available for prior years, as you mentioned, thanks again for your help.
https://ttlc.intuit.com/turbotax-support/en-us/help-article/electronic-filing/e-file-2020-2019-earli...
