Ubuntu, using st-link v2 in STM32CubeIDE: How to flash and debug

Within Ubuntu, using the st-link v2 in the STM32CubeIDE:

(1) Within the debugger setup, do I use st-link (GDB server) or st-link (open OCD)?

(2) I can compile my project though can't program or debug using the st-link v2, I just get,

"cannot exec -c /home/...*.elf

Error no such file or directory"?

Please advise