The best replacement for fldigi is digipan.

The best alternatives to fldigi are rated as following:
★★★★★  digipan
★★★  mixw
★  multipsk
★  dm780

Your alternative for fldigi is not listed? Suggest!
Speaking about fldigi, one probably shouldn't forget about signalink usb.

Other search terms related to fldigi and their ratings are:
★★★★★ signalink usb
★ n1mm
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fldigi
digipan
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