@Phaedrux, I can confirm using it (1.26.1 RRF and DWC 2.07) on my Duet 0.6

So I got this strange idea that I could probably replace Atmel SAM3X8E with SAM4E8EB-AN 144LQFP SoC which are pin to pin compatible, to be able to run the newest RRF v3 instead of an outdated and not supported anymore RRF 1.26.1 with DWC 2.07.

The reason was this sentence "version 2 uses FreeRTOS, and the additional memory requirement makes it difficult to fit both RTOS and LWIP network support into the 96Kb RAM limit of the SAM3X8E"
And so I decided to find a compatible SoC which turned out to be exactly the one that is installed on a Duet 2.

Reference:
SAM3X8E 84MHz ARM Cortex-M3 84MHz, 512KB flash (2x256KB), 96KB SRAM (64KB+32KB)
ATSAM4E8EB-AN ARM Cortex-M4 120MHz, 2KB cache, 512KB flash, 128KB SRAM, 16KB ROM

1. Will I be able to flash the RRF 3.0 using a Duet2and3Firmware-3.0.zip file from the Github repository here?
2. Should I follow "Updating from RRF 1.X or 2.x" procedure or "Updating with firmware erase" with BOSSA or SAM-BA? I assume the latter one as the SoC is new and has no firmware.
3. Do I need an 'iap4e.bin' (for Duet 2 WiFi/Ethernet) or 'iap4s.bin' (for Duet 2 Maestro) file?
4. Will it work "out if the box" with the standard configuration tool if I succeed with a firmware upgrade?

@droftarts @dc42 thank you for your answers, I'll try to sort it out. Sadly I have ordered the ICs first and then started to ask questions. For some reason I thought it should be an easy swap. Just as easy as swapping stepper drivers with klipper. So I'm currently limited to 512KB.

So I got this strange idea that I could probably replace Atmel SAM3X8E with SAM4E8EB-AN 144LQFP SoC which are pin to pin compatible, to be able to run the newest RRF v3 instead of an outdated and not supported anymore RRF 1.26.1 with DWC 2.07.

The reason was this sentence "version 2 uses FreeRTOS, and the additional memory requirement makes it difficult to fit both RTOS and LWIP network support into the 96Kb RAM limit of the SAM3X8E"
And so I decided to find a compatible SoC which turned out to be exactly the one that is installed on a Duet 2.

Reference:
SAM3X8E 84MHz ARM Cortex-M3 84MHz, 512KB flash (2x256KB), 96KB SRAM (64KB+32KB)
ATSAM4E8EB-AN ARM Cortex-M4 120MHz, 2KB cache, 512KB flash, 128KB SRAM, 16KB ROM

1. Will I be able to flash the RRF 3.0 using a Duet2and3Firmware-3.0.zip file from the Github repository here?
2. Should I follow "Updating from RRF 1.X or 2.x" procedure or "Updating with firmware erase" with BOSSA or SAM-BA? I assume the latter one as the SoC is new and has no firmware.
3. Do I need an 'iap4e.bin' (for Duet 2 WiFi/Ethernet) or 'iap4s.bin' (for Duet 2 Maestro) file?
4. Will it work "out if the box" with the standard configuration tool if I succeed with a firmware upgrade?

@Phaedrux, I can confirm using it (1.26.1 RRF and DWC 2.07) on my Duet 0.6