Wow, this new algorithm fits perfectly what I was proposing here only 4 months ago (and you also had already in your mind by then) and even more that I didn't think of!! (different curves, weighting by HFR stdev, ...) Last night I gave it a try and it went quite smooth! I can afford to make focus exposures longer to get better SNR and even so, autofocus takes way less than before. Thanks so much for your effort, for me this is quite an improvement.

Playing with the parameters I occasionally ended up with a failed autofocus, that was quite expected as I pushed some of them. But although the log reflects the failure, it doesn't show why it failed:

[2022-06-25T23:46:39.443 CEST INFO ][     org.kde.kstars.ekos.focus] - "Linear autofocus algorithm aborted."
[2022-06-25T23:46:39.445 CEST INFO ][     org.kde.kstars.ekos.focus] - "Autofocus failed, moving back to initial focus position 5.448."