Since 2021 when they started deploying the v1.5 satellites.

The only source I have ever seen is the US SDA confirming they have seen a demonstration of Starlink’s ISL, in 2024.

Do you have any more detailed or up to date information? I’m not doubting that they built ISL capabilities, since ISL is often used for collision avoidance and small scale satcom - I’m doubting that it is being actively used to route internet traffic.