Not to brigade, but netatalk seems to have recent commits, so I'm wondering how you're declaring it "abandonware." Apple has signaled an intent to migrate away from it, but they haven't done so yet. Given that I have had no success out of the box with SMB Time Machine on Core 12.0-U7, this looks bad.

21.06 PR: https://github.com/truenas/webui/pull/5507

Like I stated, people that care about AFP can stay on CORE, its only going to be removed for SCALE.

I also disagree with abandoning AFP for the "burden" it imposes. From a user perspective, you're more likely to have user support issues with SMB than AFP since Apple's AFP implementation tends to produce more stable results for Mac users than its go-it-alone SMB implementation. Even simple stuff like time machine was until recently much easier to implement in AFP on a reliable basis than SMB. 

So I reckon you will get  more user support calls and requests for help if you abandon AFP than if you  keep it thanks to Apples incompetent SMB implementation. I recently made the switch also to SMB-only as part of the TrueNAS Core upgrade but would like AFP to be supported for older systems here. The good news with AFP is that its no longer changing / evolving and hence needs little to no maintenance. It just  works. 

21.06 PR: https://github.com/truenas/webui/pull/5380