86Box is described as 'hypervisor and IBM PC system emulator that specializes in running old operating systems and software designed for IBM PC systems and compatibles from 1981 through fairly recent system designs based on the PCI bus'. There are six alternatives to 86Box for a variety of platforms, including Windows, Linux, Mac, iPhone and BSD. The best alternative is VirtualBox, which is both free and Open Source. Other great apps like 86Box are PCem (Free, Open Source), UTM (Free, Open Source), Multipass (Free, Open Source) and pcemu (Free).
Multipass is a lightweight VM manager for Linux, Windows and macOS. It's designed for developers who want a fresh Ubuntu environment with a single command. It uses KVM on Linux, Hyper-V on Windows and HyperKit on macOS to run the VM with minimal overhead.
Here you can find the original version of David Hedley's 8086 PC emulator, and my "improved" version. This will emulate a basic PC with a VGA text-only display quite well; there is a reasonable amount of software that will work with no problems.
Lima launches Linux virtual machines on macOS, with automatic file sharing, port forwarding, and containerd. Lima can be considered as a some sort of unofficial "macOS subsystem for Linux", or "containerd for Mac".