STM32F051R8 is not supported by Toolchain

Trying to build the example project from STSW-STM32117 - AN4061 EEPROM Emulation for STM32F0:

https://www.st.com/en/embedded-software/stsw-stm32117.html

Using the ST Cortex-M0/M0+ MDK version.

The project is an MDK4 project, so I installed the 'Legacy Support'

But it says the STM32F051R8 is not recognised - even though it is an ST Cortex-M0/M0+

IDE-Version:
µVision V5.33.0.0
Copyright (C) 2020 ARM Ltd and ARM Germany GmbH. All rights reserved.


Tool Version Numbers:
Toolchain:          MDK-ARM Cortex-M0/M0+ for ST  Version: 5.33.0.0
Toolchain Path:     C:\apps\Keil\MDK533_ST\ARM\ARMCC\Bin
C Compiler:         Armcc.exe            V5.06 update 7 (build 960)
Assembler:          Armasm.exe           V5.06 update 7 (build 960)
Linker/Locator:     ArmLink.exe          V5.06 update 7 (build 960)
Library Manager:    ArmAr.exe            V5.06 update 7 (build 960)
Hex Converter:      FromElf.exe          V5.06 update 7 (build 960)
CPU DLL:            SARMCM3.DLL          V5.33.0.0
Dialog DLL:         TARMCM1.DLL          V1.14.3.0
Target DLL:         STLink\ST-LINKIII-KEIL_SWO.dll      V3.0.8.0
Dialog DLL:         TARMCM1.DLL          V1.14.3.0