Raspi4のUbuntu64でadd architecture armhfしてラズパイ用のmathematicaが実行できた。
ただし、keygen必要。

Out[2]//InputForm=
{"MachineName" -> "ubuntu", "System" -> "Linux ARM (32-bit)",
"BenchmarkName" -> "WolframMark", "FullVersionNumber" -> "12.1.1",
"Date" -> "December 24, 2020", "BenchmarkResult" -> 0.206,
"TotalTime" -> 67.311, "Results" -> {{"Data Fitting", 2.757},
{"Digits of Pi", 1.616}, {"Discrete Fourier Transform", 10.401},
{"Eigenvalues of a Matrix", 3.524}, {"Elementary Functions", 5.119},
{"Gamma Function", 2.196}, {"Large Integer Multiplication", 2.28},
{"Matrix Arithmetic", 1.637}, {"Matrix Multiplication", 10.93},
{"Matrix Transpose", 4.91}, {"Numerical Integration", 2.502},
{"Polynomial Expansion", 0.339}, {"Random Number Sort", 1.19},
{"Singular Value Decomposition", 8.676}, {"Solving a Linear System", 9.234}}}