I really like xv6 for its simplicity and restricted scope. It feels like a better Minix in the sense of being a codebase intended for university coursework. If your goal is learning the very basics of what an OS does, xv6 is a good place to start. ToaruOS can cover the same ground - of course there's paging and IPC and threads - but I don't have a cache of PDFs sitting around describing it, and there's no intentionally missing bits waiting for a student to fill them in for homework. If xv6 is "Operating Systems 101", then ToaruOS is a 300-level seminar/workshop.
My intended audience is hobbyists who are looking for a reference for writing their own OS - the sort of people we often find on osdev.org, or the #osdev channel on Libera, who have stumbled through an old tutorial on x86 bring-up and want some example of how "the next steps" work.
I wouldn't say I "own" that channel in any respect, I'm just responsible for dragging it over from Freenode during the exodus... we've got the same same staff as we did before the move and I'm not even the "founder" according to ChanServ.
When I started the project a decade ago, my aim was specifically to understand POSIX/Unix and to "learn by doing", so of course there's some POSIX-like elements underpinning the design. Back before I decided that literally anything can be in scope and was using third-party components, this aided in porting software, as other commenters have pointed out. These days, it gives more purpose to things I build for the OS if they can also reasonably be built for Linux or macOS - things like my editor (which I wrote for the OS and now use as my daily driver in Linux), or my Python knock-off.
As for the microkernel bit, this might sound like circular reasoning but I didn't go for a microkernel because no one really uses microkernels. It's not that I think microkernels are a bad idea, ToaruOS does push plenty of stuff into userspace. Rather, my main goal at the moment is to provide an educational resource that more accurately models the way "real" OSes work than the typical academic OS projects.
My intended audience is hobbyists who are looking for a reference for writing their own OS - the sort of people we often find on osdev.org, or the #osdev channel on Libera, who have stumbled through an old tutorial on x86 bring-up and want some example of how "the next steps" work.