If you e-file a return, you do not physically "sign" it. Your signature is electronic when you enter your 2019 AGI to identify yourself to the IRS as the same person who used that SSN for a 2019 return. You can only e-file a 2020 return. No other years can be e-filed.
If you want to print your return to mail in, you have to figure out your own printer problems.
I DO NOT HAVE A PRINTER—WHAT CAN I DO?
We cannot solve your printer problem for you If you do not have a working printer, you can access your account from any computer that has internet access and print your return. So perhaps you need to see if a friend or relative can let you print from a computer with a printer. Or print it at a UPS place or Staples, etc.