Which version of which toolchain are you using, and which version of zephyr?

Everything is a recent install.
zephyr-sdk-0.13.0

Version of zephyr I'm using:

commit fcfe597e5dadb96ecef5d6e8c82ffc99b5f4d59c (HEAD -> main, origin/main, origin/HEAD)
Author: Iuliana Prodan <iuliana.prodan@...>
Date:   Sat Aug 28 01:08:19 2021 +0300

OK, so now I checkout tag zephyr-v2.6.0.

Then I do

rm -rf build

mkdir build

cd build

cmake ..

I get

Including boilerplate (Zephyr base): /home/pi/zephyrproject/zephyr/cmake/app/boilerplate.cmake
CMake Deprecation Warning at /home/pi/zephyrproject/zephyr/cmake/app/boilerplate.cmake:37 (cmake_policy):
  The OLD behavior for policy CMP0079 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.

I had that before, though.

My errors are now:

Parsing /home/pi/zephyrproject/zephyr/Kconfig
/home/pi/zephyrproject/zephyr/scripts/kconfig/kconfig.py: /home/pi/zephyrproject/my_blinky/build/Kconfig/Kconfig.modules:2: Could not open '/home/pi/zephyrproject/zephyr/' (in 'osource "$(ZEPHYR_CANOPENNODE_KCONFIG)"') (EISDIR: Is a directory)
CMake Error at /home/pi/zephyrproject/zephyr/cmake/kconfig.cmake:264 (message):
  command failed with return code: 1
Call Stack (most recent call first):
  /home/pi/zephyrproject/zephyr/cmake/app/boilerplate.cmake:565 (include)
  /home/pi/zephyrproject/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:24 (include)
  /home/pi/zephyrproject/zephyr/share/zephyr-package/cmake/ZephyrConfig.cmake:35 (include_boilerplate)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!