Boards like the ESP32-C6, almost 5 years old, are not supported in PlatformIO with Arduino libraries, because they refuse to update the Arduino core in some kind of stand-off with Espressif. This has been going on for years. There is a fork [1] that offers support but none of it makes back upstream.
As a hobbyist I've given up on PIO and moved to a barebones arduino-cli setup instead. Much lighter and less painful.
ESP-IDF, the official C SDK, is a bit more work, and there is drama around platform-io, but it’s significantly more stable.