Makes sense. The commits are ordered to build things up progressively under distinct sub-topics, hopefully this offers a feasible way in. Happy to respond to any queries if that can save you time.

Calling Brooks?

Hi Brookes, I added a small tweak for your review a couple of months ago, but the system is still labelling it as "Unsubmitted" for some reason, so I think you haven't seen it, could you take a look?

Config file tweak, NOTES update.

I have resubmitted with the addition to HISTORY you suggested.

Reusing existing syscall numbers
Removal of new syscall numbers, reusing old ones instead, with
associated changes to ensure backward compatibility, as per discussion.

Thanks for that. I have it working now. I am ready to "git arc update" if you are happy with my response to your comment regarding the man (2) page

Hi Brooks. Am very happy to remove the need to change syscalls numbers, did not realise that was possible when the symbol itself (the name) changed. As suggested I removed the old symbols from Symbol.map, put the new names under the original numbers in syscalls.master, and to compat.h added:
sym_compat(ffclock_setestimate, freebsd15_ffclock_setdata, FBSD_1.3);
sym_compat(ffclock_getestimate, freebsd15_ffclock_getdata, FBSD_1.3);
which was the only option that made sense to me that was consistent with existing entries. Does this look right?