Do thermal label printers need ink or toner?

No. The 4x6 shipping printers here (Phomemo, JADENS, Nelko, and similar) use direct thermal technology, which burns the image onto heat-sensitive label stock with no ink, toner or ribbon. The trade-off reviewers note is that thermal labels can fade over time and are not ideal for long-term archival use, but for shipping that is rarely a problem.