This is a GIST that will help you complile MagTag firmware in ESPHome while platformIO is in a transitional state.

esphome-magtag.yaml

substitutions:
  devicename: magtag
  upper_devicename: Magtag


esphome:
  name: magtag
  platform: esp32
  board: esp32dev
  platformio_options:
    platform:
      - https://github.com/platformio/platform-espressif32.git#feature/arduino-upstream
    platform_packages:
      - framework-arduinoespressif32 @ https://github.com/espressif/arduino-esp32.git#2.0.0-rc1
      - platformio/tool-esptoolpy @ ~1.30100
      - espressif/toolchain-xtensa-esp32 @ 8.4.0+2021r1
    board_build.mcu: esp32s2
logger:
api:
ota:
  password: !secret ota_password
wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

thanks for sharing, can you confirm how you were able to flash the magtag? i cannot download an image, i just the following??. thanks

INFO Reading configuration /config/esphome/magtag-01.yaml...
INFO Generating C++ source...
INFO Compiling app...
Processing magtag-01 (board: esp32dev; framework: arduino; platform: 
https://github.com/platformio/platform-espressif32.git#feature/arduino-upstream)
--------------------------------------------------------------------------------
Configuring from remote
* Adding toolchain toolchain-riscv32-esp with version 8.4.0+2021r1
* Adding toolchain toolchain-xtensa-esp32 with version 8.4.0+2021r1
* Adding toolchain toolchain-xtensa-esp32s2 with version 8.4.0+2021r1
Tool Manager: Installing espressif/toolchain-xtensa-esp32s2 @ 8.4.0+2021r1
Error: Could not find the package with 'espressif/toolchain-xtensa-esp32s2 @ 8.4.0+2021r1' requirements for your system 'linux_aarch64'

I think this is outdated at this point, a lot has changed since I posted this and there is almost certainly a better way. It looks to me that the library required is not available for your system which appears to be 64bit arm. If you have access to an x86 system I would give that a try. I am not very involved in the Arduino/platformio world so I don't have any more insight.

This GitHub issue may be of some help to you. esphome/feature-requests#996