Are we asking about a late 2020 return or planning for a 2021 return?
Head of household might be allowed if you have not shared a home with your spouse for all of the second half of the tax year. However, if you returned to your home country and spent time with your spouse, that might defeat HOH. I would be very cautious about that approach.
You can file a joint return if you apply for an ITIN for your spouse. You would print your joint return and mail it to the IRS along with a form W-7 ITIN application. You must include proof of identity as required by the ITIN application and your spouse must sign the printed tax return, so you may need to involve international mail or an express service to send those documents back and forth. Once you get the signed W-7, the proof of identity and the signed tax return, mail them to the IRS office in the W-7 instructions. After they issue the ITIN, they will forward the tax returns for processing.
