In the last day, I have been amazed at the results with non-resonant antennas on FT8 RX. May be I shouldn't be.
On 160m FT8 RX one often has to add attenuation and, as long as the S/N is fine, it will still get results.
On 15m FT8 RX, I guess my 10m antenna is a few dBs down, but as long as the S/N is sufficient I will still get decodes.