6900 kHz is the “home channel” (I’ve heard it literally referred to as “canale de la casa”) for Spanish language freebanders operating in this portion of the spectrum. They have a freeband 11 meter CB-like operating practice, including the use of 5 kHz channel steps and use of the LSB/USB mode switch as a way to find a clear channel. Most of their stuff seems to be in LSB though.
This differs from the other Spanish language - and Portuguese language QSOs heard in this band...the other stations seem to just pick a frequency and go (6919 kHz, 6925 kHz, 6933 kHz, 6952 kHz, etc. etc.). The 6900 LSB group(s) are almost certainly radio hobbyists operating out of band vs. fishing fleets or drug smugglers using unconventional HF frequencies and bands for their long-range communications needs.
6900 LSB seems to be active almost nightly, especially when 11 meters is totally dead.