I am using stm32 version 2.8.1, which I have updated to this new version via the Arduino IDE.
Microsoft Visual Studio Community 2022 (64-bit) - Current version 17.10.5
Arduino IDE for Visual Studio 2022 2024.722.2208.

A link error occurred:
Linking it all together ...
arm-none-eabi-gcc\13.2.1-1.1/bin/arm-none-eabi-gcc" -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb -Os -DNDEBUG --specs=nano.specs -Wl,--defsym=LD_FLASH_OFFSET=0x0 -Wl,--defsym=LD_MAX_SIZE=262144 -Wl,--defsym=LD_MAX_DATA_SIZE=65536 -Wl,--cref -Wl,--check-sections -Wl,--gc-sections -Wl,--entry=Reset_Handler -Wl,--unresolved-symbols=report-all -Wl,--warn-common /ldscript.ld" \hardware\stm32\2.8.1\system/ldscript.ld" nF4\Debug/Saxo2.ino.map" -Wl,--no-warn-rwx-segments -o /Saxo2.ino.elf" ug" -Wl,--start-group "Saxo2.cpp.o" "src\CirquePinnacle.cpp.o" "src\MIDI.cpp.o" "VM_DBG\VM_DBG.cpp.o" "VM_DBG\VM_mem_check_sam.cpp.o" "SPI\SPI.cpp.o" "SPI\utility\spi_com.c.o" "Wire\Wire.cpp.o" "Wire\utility\twi.c.o" "Adafruit_BNO08x\sh2.c.o" "Adafruit_BNO08x\sh2_SensorValue.c.o" "Adafruit_BNO08x\sh2_util.c.o" "Adafruit_BNO08x\shtp.c.o" "Adafruit_BNO08x\Adafruit_BNO08x.cpp.o" "Adafruit_BusIO\Adafruit_BusIO_Register.cpp.o" "Adafruit_BusIO\Adafruit_I2CDevice.cpp.o" "Adafruit_BusIO\Adafruit_SPIDevice.cpp.o" "Adafruit_Unified_Sensor\Adafruit_Sensor.cpp.o" "SrcWrapper\syscalls.c.o" "SrcWrapper\HardwareTimer.cpp.o" "SrcWrapper\new.cpp.o" "SrcWrapper\HAL\stm32yyxx_hal.c.o" "SrcWrapper\HAL\stm32yyxx_hal_adc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_adc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_can.c.o" "SrcWrapper\HAL\stm32yyxx_hal_cec.c.o" "SrcWrapper\HAL\stm32yyxx_hal_comp.c.o" "SrcWrapper\HAL\stm32yyxx_hal_comp_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_cordic.c.o" "SrcWrapper\HAL\stm32yyxx_hal_cortex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_crc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_crc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_cryp.c.o" "SrcWrapper\HAL\stm32yyxx_hal_cryp_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dac.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dac_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dcache.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dcmi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dcmi_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dfsdm.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dfsdm_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dma.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dma2d.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dma_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dsi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_dts.c.o" "SrcWrapper\HAL\stm32yyxx_hal_eth.c.o" "SrcWrapper\HAL\stm32yyxx_hal_eth_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_exti.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fdcan.c.o" "SrcWrapper\HAL\stm32yyxx_hal_firewall.c.o" "SrcWrapper\HAL\stm32yyxx_hal_flash.c.o" "SrcWrapper\HAL\stm32yyxx_hal_flash_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_flash_ramfunc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fmac.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fmpi2c.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fmpi2c_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fmpsmbus.c.o" "SrcWrapper\HAL\stm32yyxx_hal_fmpsmbus_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gfxmmu.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gfxtim.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gpio.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gpio_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gpu2d.c.o" "SrcWrapper\HAL\stm32yyxx_hal_gtzc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_hash.c.o" "SrcWrapper\HAL\stm32yyxx_hal_hash_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_hcd.c.o" "SrcWrapper\HAL\stm32yyxx_hal_hrtim.c.o" "SrcWrapper\HAL\stm32yyxx_hal_hsem.c.o" "SrcWrapper\HAL\stm32yyxx_hal_i2c.c.o" "SrcWrapper\HAL\stm32yyxx_hal_i2c_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_i2s.c.o" "SrcWrapper\HAL\stm32yyxx_hal_i2s_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_i3c.c.o" "SrcWrapper\HAL\stm32yyxx_hal_icache.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ipcc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_irda.c.o" "SrcWrapper\HAL\stm32yyxx_hal_iwdg.c.o" "SrcWrapper\HAL\stm32yyxx_hal_jpeg.c.o" "SrcWrapper\HAL\stm32yyxx_hal_lcd.c.o" "SrcWrapper\HAL\stm32yyxx_hal_lptim.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ltdc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ltdc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_mdf.c.o" "SrcWrapper\HAL\stm32yyxx_hal_mdios.c.o" "SrcWrapper\HAL\stm32yyxx_hal_mdma.c.o" "SrcWrapper\HAL\stm32yyxx_hal_mmc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_mmc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_nand.c.o" "SrcWrapper\HAL\stm32yyxx_hal_nor.c.o" "SrcWrapper\HAL\stm32yyxx_hal_opamp.c.o" "SrcWrapper\HAL\stm32yyxx_hal_opamp_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ospi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_otfdec.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pccard.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pcd.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pcd_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pka.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pssi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pwr.c.o" "SrcWrapper\HAL\stm32yyxx_hal_pwr_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_qspi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ramcfg.c.o" "SrcWrapper\HAL\stm32yyxx_hal_ramecc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rcc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rcc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rng.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rng_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rtc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_rtc_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sai.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sai_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sd.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sdadc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sdram.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sd_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_smartcard.c.o" "SrcWrapper\HAL\stm32yyxx_hal_smartcard_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_smbus.c.o" "SrcWrapper\HAL\stm32yyxx_hal_smbus_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_spdifrx.c.o" "SrcWrapper\HAL\stm32yyxx_hal_spi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_spi_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_sram.c.o" "SrcWrapper\HAL\stm32yyxx_hal_subghz.c.o" "SrcWrapper\HAL\stm32yyxx_hal_swpmi.c.o" "SrcWrapper\HAL\stm32yyxx_hal_tim.c.o" "SrcWrapper\HAL\stm32yyxx_hal_tim_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_tsc.c.o" "SrcWrapper\HAL\stm32yyxx_hal_uart.c.o" "SrcWrapper\HAL\stm32yyxx_hal_uart_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_usart.c.o" "SrcWrapper\HAL\stm32yyxx_hal_usart_ex.c.o" "SrcWrapper\HAL\stm32yyxx_hal_wwdg.c.o" "SrcWrapper\HAL\stm32yyxx_hal_xspi.c.o" "SrcWrapper\LL\stm32yyxx_ll_adc.c.o" "SrcWrapper\LL\stm32yyxx_ll_bdma.c.o" "SrcWrapper\LL\stm32yyxx_ll_comp.c.o" "SrcWrapper\LL\stm32yyxx_ll_cordic.c.o" "SrcWrapper\LL\stm32yyxx_ll_crc.c.o" "SrcWrapper\LL\stm32yyxx_ll_crs.c.o" "SrcWrapper\LL\stm32yyxx_ll_dac.c.o" "SrcWrapper\LL\stm32yyxx_ll_delayblock.c.o" "SrcWrapper\LL\stm32yyxx_ll_dlyb.c.o" "SrcWrapper\LL\stm32yyxx_ll_dma.c.o" "SrcWrapper\LL\stm32yyxx_ll_dma2d.c.o" "SrcWrapper\LL\stm32yyxx_ll_exti.c.o" "SrcWrapper\LL\stm32yyxx_ll_fmac.c.o" "SrcWrapper\LL\stm32yyxx_ll_fmc.c.o" "SrcWrapper\LL\stm32yyxx_ll_fmpi2c.c.o" "SrcWrapper\LL\stm32yyxx_ll_fsmc.c.o" "SrcWrapper\LL\stm32yyxx_ll_gpio.c.o" "SrcWrapper\LL\stm32yyxx_ll_hrtim.c.o" "SrcWrapper\LL\stm32yyxx_ll_i2c.c.o" "SrcWrapper\LL\stm32yyxx_ll_i3c.c.o" "SrcWrapper\LL\stm32yyxx_ll_icache.c.o" "SrcWrapper\LL\stm32yyxx_ll_lpgpio.c.o" "SrcWrapper\LL\stm32yyxx_ll_lptim.c.o" "SrcWrapper\LL\stm32yyxx_ll_lpuart.c.o" "SrcWrapper\LL\stm32yyxx_ll_mdma.c.o" "SrcWrapper\LL\stm32yyxx_ll_opamp.c.o" "SrcWrapper\LL\stm32yyxx_ll_pka.c.o" "SrcWrapper\LL\stm32yyxx_ll_pwr.c.o" "SrcWrapper\LL\stm32yyxx_ll_rcc.c.o" "SrcWrapper\LL\stm32yyxx_ll_rng.c.o" "SrcWrapper\LL\stm32yyxx_ll_rtc.c.o" "SrcWrapper\LL\stm32yyxx_ll_sdmmc.c.o" "SrcWrapper\LL\stm32yyxx_ll_spi.c.o" "SrcWrapper\LL\stm32yyxx_ll_swpmi.c.o" "SrcWrapper\LL\stm32yyxx_ll_tim.c.o" "SrcWrapper\LL\stm32yyxx_ll_ucpd.c.o" "SrcWrapper\LL\stm32yyxx_ll_usart.c.o" "SrcWrapper\LL\stm32yyxx_ll_usb.c.o" "SrcWrapper\LL\stm32yyxx_ll_utils.c.o" "SrcWrapper\stm32\bootloader.c.o" "SrcWrapper\stm32\clock.c.o" "SrcWrapper\stm32\core_callback.c.o" "SrcWrapper\stm32\dwt.c.o" "SrcWrapper\stm32\hw_config.c.o" "SrcWrapper\stm32\otp.c.o" "SrcWrapper\stm32\pinmap.c.o" "SrcWrapper\stm32\PortNames.c.o" "SrcWrapper\stm32\stm32_def.c.o" "SrcWrapper\stm32\system_stm32yyxx.c.o" "SrcWrapper\stm32\timer.c.o" "SrcWrapper\stm32\uart.c.o" "SrcWrapper\stm32\analog.cpp.o" "SrcWrapper\stm32\interrupt.cpp.o" "USBDevice\usbd_conf.c.o" "USBDevice\usbd_desc.c.o" "USBDevice\usbd_ep_conf.c.o" "USBDevice\usbd_if.c.o" "USBDevice\usb_device_core.c.o" "USBDevice\usb_device_ctlreq.c.o" "USBDevice\usb_device_ioreq.c.o" "USBDevice\USBSerial.cpp.o" "USBDevice\cdc\cdc_queue.c.o" "USBDevice\cdc\usbd_cdc.c.o" "USBDevice\cdc\usbd_cdc_if.c.o" "USBDevice\hid\usbd_hid_composite.c.o" "USBDevice\hid\usbd_hid_composite_if.c.o" "variant\generic_clock.c.o" "variant\PeripheralPins.c.o" "variant\PeripheralPins_BLACKPILL_F401Cx.c.o" "variant\PeripheralPins_PYBSTICK26_LITE.c.o" "variant\variant_BLACKPILL_F401Cx.cpp.o" "variant\variant_generic.cpp.o" "variant\variant_PYBSTICK26_LITE.cpp.o" \core.a" -lc -Wl,--end-group -lm -lgcc -lstdc++
ld.exe: \Debug\\core.a(HardwareSerial.cpp.o).bss.Serial2+0x0): multiple definition of Serial2; Saxo2.cpp.o:(.bss.Serial2+0x0): first defined here
 
ld.exe: Saxo2.cpp.o: in function __static_initialization_and_destruction_0()
Saxo2.ino: (.text._Z41__static_initialization_and_destruction_0v+0x3c): undefined reference to Serial1
 
collect2.exe*: error: ld returned 1 exit status

Error linking for board Generic STM32F4 series(STMicroelectronics_GenF4)
Debug build failed for project 

The error disappeared after I switched the toolbar from Debug to Release.
It also disappeared after I switched the toolbar from Release to Debug again.