I have to upload a signed copy of my 2021 returns fro college financial aid applications for my son but the only file available on TurboTax is an unsigned version.

When you e-file there is no physical signature on the Form 1040.   You "signed" electronically by entering your AGI or PIN.  If someone wants a "signed" copy take out a pen and sign it on the line that says "Sign here."

Yep ... there is no INK signature when you efile ... so you will need to download the PDF.  Print off the 1040, ink sign in on page 2,  put it back in the PDF to send to FASFA.