Yes.
As long as your 2019 returns were filed and accepted by the IRS, you can go ahead and prepare the amended return. You are correct that it will take a bit longer to process.
IRS operations are limited during the Covid-19 pandemic. Attached is a link with more information as to what departments are available to contact at the moment. Once the restrictions are lifted, the IRS will resume processing returns that have been mailed in.
IRS operations
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