Compiling/Installing
https://github.com/ptitSeb/box64/blob/main/docs/COMPILE.md

Box64 0.3.0: x86_64 emulator for Linux supports AVX and AVX2
Box64 emulates x64_64 CPUs in non-x86 Linux versions. The new version 0.3.0 supports the vector instruction set extensions AVX and AVX2.

Box64 - Linux Userspace x86_64 Emulator with a twist, targeted at ARM64, RV64 and LoongArch Linux devices
https://github.com/ptitSeb/box64

 

Thanx Plendix

 

Raspberry Pi uses ARM CPUs.

box86 is for emulating x86 CPUs on ARM CPUs.
box64 is for emulating x64 CPUs on ARM CPUs.

Raspberry Pis aren't crazy fast, emulating x86/x64 on a Pi usually isn't a hot idea for realtime audio.

Linux packages say what they're useable on in their file name (dingdong-linux-aarch64-etc.etc vs dingdong-linux-x64-etc.etc). You can't take a x86/x64 package and run it on a Pi (aarch64) without many extra steps - which slow down the execution of the software by considerable amounts.

If a company only offers Linux x64 packages and no Linux aarch64 packages for your plugin, you're out of luck and need to look elsewhere (or shoot them a mail and ask if they could provide aarch64 binaries).

If a plugin is available in source form, there's a good chance it can be compiled (by you) to run natively on your aarch64 Pi. If the software uses x86/x64 machine instructions, you will need to figure out how to translate those into aarch64 instructions; either by rewriting that part of the code or by integrating a shim that does (part of) the work for you (sse2neon for example). Neither approach is trivial.