Pio debug with STM32 blackmagic does not connect

I’m trying to use piodebuggdb on a custom stm32 board with a BMP and while GDB starts it does not connect to the target. Uploading via the BMP works fine and I can also run gdb manually. Where should the gdb start-up commands come from that contain the target command, etc. I see where that’s defined in the platform for the upload but where is it defined for debug?

Here is what I get:

tve@soumak /h/s/g/g/hello> piodebuggdb -e arduino
PIO Plus (https://pioplus.com) v1.4.5
Preparing firmware for debugging...
Processing arduino (platform: ststm32; board: jnz5_l082kz; framework: arduino)
----------------------------------------------------------------------------------------------------
Verbose mode can be enabled via `-v, --verbose` option
PLATFORM: ST STM32 > JNZ5-L082
SYSTEM: STM32L082KZ 32MHz 20KB RAM (192KB Flash)
DEBUG: CURRENT(blackmagic) EXTERNAL(blackmagic, stlink)
Converting hello.ino
...
...
Building .pioenvs/arduino/firmware.bin
Checking size .pioenvs/arduino/firmware.elf
Memory Usage -> http://bit.ly/pio-memory-usage
DATA:    [==        ]  18.8% (used 3848 bytes from 20480 bytes)
PROGRAM: [==        ]  24.4% (used 48008 bytes from 196608 bytes)
=================================== [SUCCESS] Took 2.17 seconds ===================================

============================================ [SUMMARY] ============================================
Environment arduino     [SUCCESS]
Environment arduino-oc1 [SKIP]
=================================== [SUCCESS] Took 2.17 seconds ===================================
Reading symbols from /home/src/goobies/goobies/hello/.pioenvs/arduino/firmware.elf...done.
(gdb)
(gdb) start
Don't know how to run.  Try "help target".
(gdb)

Also:

tve@soumak /h/s/g/g/hello> pio device list
/dev/ttyS0
----------
Hardware ID: PNP0501
Description: ttyS0

/dev/ttyACM1
------------
Hardware ID: USB VID:PID=1D50:6018 SER=D5CCC7D6 LOCATION=1-2.4.4:1.2
Description: Black Magic Probe (HyTiny), (Firmware v1.6-rc0-453-g10b274a-dirty) - Black Magic UART Port

/dev/ttyACM0
------------
Hardware ID: USB VID:PID=1D50:6018 SER=D5CCC7D6 LOCATION=1-2.4.4:1.0
Description: Black Magic Probe (HyTiny), (Firmware v1.6-rc0-453-g10b274a-dirty) - Black Magic GDB Server

There is no start command for GDB. See 2-nd example Redirecting...

pio debug -e arduino --interface=gdb -x .pioinit
(gdb) continue