Using APFS on HDDs in 2023?

AFAIK, Apple has not updated APFS, specifically for HDDs. As you already know, it was designed to work best with SSDs.

From my experience, I try to stick with APFS for SSDs & HFS+ for HDDs as I have a mix of Apple hardware dating back to 2008. Regardless, I have not found any adverse affects of formatting HDDs for APFS, even if these drives are "dedicated" for Time Machine backups.

I have seen content in this community and on the broader web that indicates that formatting a HDD using APFS is not a smart thing to do. The reasoning being that the way APFS handles file changes creates a large number of small file fragments which on a HDD take longer to read. The articles I have seen all seem to be from 2017 when APFS was young.

Has Apple updated APFS so it works better with HDDs? Are there any more recent evaluations like in 2022 or 2021 ?

I doubt they would ever bother. The process of managing the sectors on an SSD would slow down that process.

The only reason that would become a problem is if you are editing large files, like movies, or images, as it would be doing a lot of loading into memory then writing back to disk. Using APFS on an HDD for one time writes, like Time Machine, would not cause fragmentation.