For Lightspeed eCom: see SQL/Power BI connector for Lightspeed eCom (C-series).
For Lightspeed Restaurant K-series: see SQL/Power BI connector for Lightspeed Restaurant K-series
For Lightspeed Restaurant U-series: see SQL/Power BI connector for Lightspeed Restaurant U-series (Upserve)
No links for Lightspeed R-Series and O-Series.
Documentation available at (published by Lightspeed):
https://www.postman.com/lightspeedhq/l-series-api/overview
Authentication always OAuth. Functionality similar to Horeko (Master data on Horeko and over 75 other platforms, 180 days free).