Re: What's "Arm compatible" mean?
The first sentence has a weird phrase, "Arm-compatible". What's that mean... there have been many ARM micro-architectures
Also, without knowing the version of the ABI, or what coprocessor features are present (NEON for example) it's very hard to say.... Look at the work RISC OS has to do to keep up with various different flavours of ARM SoCs, and they're just concerned with 32bit, not 64.
And the Amazon Graviton2 is a licensed Arm Neoverse CPU, in exactly the same way as the Apple things are and the Samsung Exynos processors
Pedant: Samsung yes, Apple no. Apple and Qualcomm have architecture licences and design their own CPU cores from scratch (eg, 'Thunder' and 'Lightening' from Apple, or 'Krait' and 'Kryo' from Qualcomm), rather than using an Arm designed core and adding the rest like core licencees do. (Samsung, Amazon, et al.)