Some architectures are better for pedagogy (learning) while still covering the important concepts. RISC-V or MIPS fit this well. RISC-V is also not patent encum

Some architectures are better for pedagogy (learning) while still covering the important concepts. RISC-V or MIPS fit this well. RISC-V is also not patent encumbered so anyone can freely use it. Some platforms are not great pedagogically, but are taught because they are used in industry, like x86. ARM manages to be ok at both. I don't see a point in learning with other architectures.