From your previous post, here, you have a U.S.A. carrier minority variant S20 in Pakistan.
You cannot swap U.S.A. and Global firmwares.
The USA model has a Snapdragon chip and therefore not compatible with the Global model's Exynos chip so you cannot simply flash a dual SIM Global firmware.
Also, the U.S.A. Snapdragon models will not operate outside the U.S. on the worldwide 5G networks.
Furthermore, depending on which of the U.S. models you have, your phone may not receive any future firmware updates.
TOP TIP: Always choose a model of phone for the country/region you are using it in.
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My device... Galaxy S21 Ultra 5G 16/512GB (G998B D/S) CSC=BTU
