Thanks for mentiong focus-stack, it’s not only nice, it’s awesome! Its image-alignment is not only faster but also much more accurate, I have a few cases where align_image_stack failed horribly but focus-stack handles easily. The stacking is also quite good but I still give enfuse an edge here. I still say it’s awesome because it’s a modern approach, utilizing OpenCV, lots of potential. On my GTX 3060, it took only 11 seconds to stack 23 images (the dragon below).
I was about to add cpfind as an alternative to align_image_stack, but after testing out focus-stack and noticing that it uses OpenCV’s ECC algorithm for alignment, I got too excited that I spent the whole night adding ECC to mftker (Tkinter is definitely not multiprocessing-friendly). Even with just 10 iterations and termination-eps of 1e-7, about 22-24 second per image-pair, the result is much better than align_image_stack.
Here is an example where ais failed:
and ECC handled with ease
Took a few hours to learn how to use multiprocesssing.Pool, I pick the middle image as anchor and align the rest against it. Memory consumption is a limit though. I tested using all 16 cores on my Ryzen 5700H, and 32GB memory quickly got flooded into swap 
I’d say 4-8 processes is safe for 24MP images, not too bad for a Python implementation.
Now that I started adding different tools into my little script, I’d love to add focus-stack as another option for alignment (since it’s faster and more efficient than Python implementation). I’ll probably contact the author to see if s/he can expose more options, such as the number of iterations, eps, …, and having a stack-only mode.
Another possibility is median-stacking. I did a few manually before, and the workflow is very similar to focus stacking. So tempting to rename the current “Stack” tab to “Focus Stack”, and add another tab “Median Stack” 
In term of stacking quality, focus-stack is able to address halo somewhat, but still has faint ghosting in the bigger radius. Its output also has less contrast/saturation/details than enfuse. But as I said, anything with a modern approach is more than welcomed.
For comparison, here’s enfuse stacking with no mask:
focus-stack stacking (faint ghosting outlines):
enfuse with a few exclude masks on the extreme out-of-focus areas:
enfuse with include masks on every image:
focus-stack with masks 
another one by enfuse (that align_image_stack failed)
enfuse with a few exclude masks at the extreme ends
and focus-stack addresses halo pretty well
