@imaltesers ,
1. yes indeed , you can file joint and be able to take a deduction for foreign taxes paid, assuming that (a) you itemize; (b) your total foreign tax plus any state taxes withheld for your spouse, plus property taxes are total less than 10,000 ( SALT limit ) and of course (c) your total itemized deduction is greater than 24,800. For most people it does not work and so they stay with standard deduction.
2. Note that if your AGI changes with the foreign income, then you should file an amended return after the the original return has been processed ( your refund issued is a stand-in). Although in your particular case there is probably no way for the IRS to be aware of this --- but .....
3. If I remember right generally 4/15 ( I don't know if this is also extended this year) is the deadline after which one cannot change from MFJ to MFS, even as an amended return.
4. Please also note that during 2020 if you had a foreign bank account you would come under FBAR and FATCA rules
Stay safe
pk
