What exactly is the openD Canon D split about, and as a regular person, which one should I use? Any other details you could give, or background? I haven't followed any of that and have no clue.

I have no confidence left in the leadership of old D. This is an example: porting druntime to emscripten wasn't actually that hard to do, I did it in about a week of spare time in between kid and day job. Their solution, in so much as they pay attention to it at all, is to just point at betterC which remains half-assed for about a decade now (search my blog archives, here's one with them talking about "A betterC standard library" from December 2016 - https://arsdnet.net/this-week-in-d/2016-dec-18.html - and none of that has materialized ).

You might say if it is so easy, why not do it upstream? It takes years of political arguments and random ghosting to get anything done up there, all while constant (regression inducing) code churn breaks your PRs every other month, so you spend 3x the time rebasing than you ever spent writing the implementation before it is merged...... if it ever gets merged at all. I have several successful contributions to upstream D, it happens, but most the work done there is ignored. You might get some encouraging forum replies, but when it comes time to ship it? Crickets. Several former D contributors jumped ship for Zig many years ago, and it was a real loss for us (and real gain for them).

With the opend, I know if it works and delivers real world value, I can ship a release, dmd and ldc together, so minimal duplicated waste work.

What should you use? idk, opend is basically my pet project, provided in the hope that it will be useful, but THIS SOFTWARE IS PROVIDED `'AS IS″ AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE so your mileage may vary. Still, I maintain about a half million lines of code, some of which is quite old, so keeping some stability is important to me while moving forward with select common-sense, incremental improvements. Most D code works fine either way though, I've done web programming a long time, in the old school tradition, so words like "progressive enhancement" and "graceful degradation" are meaningful to me, even when being a compiler maintainer.