Some undefined references
yes, your linker is not modified. but the error message indicates that you have data at address 0 & 26964.
This address range is not located within flash which explains the warning “no flash bank found for address 0 / 26946”.
to verify could you please attach the map file (~/Debug/output.map)
maybe you are not pointing to this linker, check (Project > Properties > C/C++ Build > Settings > MCU GCC Linker > General > Linker flags > Linker Script (-T) )
;){kind=link}