I finally got around to giving this a go and managed to get it working. I should note that I have the STLINK-V3MINIE (the usb-c version).
I found the grounds on the debug header and compared to the pins on the seed schematic and it appeared to have the same layout, so red stripe on the side with the white lines in the corner (i.e. red stripe on the other side to the reset/boot buttons).
I had a few issues getting it going on the software side (on macOS) so first confirmed that it worked with the STM32CubeProgrammer app and then the openocd command line tool.
In the end I used open-ocd 0.12.0-rc2 (installed via Homebrew) but for some reason I ended up with two different versions of open-ocd (one in the brew dir, one in /usr/local/share) so when running make commands I had to override OCD_DIR=/opt/homebrew/share/openocd/scripts (as this is hardcoded to /usr/local/share/openocd/scripts in libDaisy) but I didn’t need to do that when running the debugger from VS Code for some reason.
Hope that helps.
@ohthepain are you getting any particular errors?