pcmanfm-qt

I'm partial to pcmanfm-qt, which also supports splits, and has the best "search in current directory" I've seen anywhere. You open a directory, start typing, and it filters out matching files fzf-style. It doesn't simply select them like some other file managers do, it searches within the name and not just the prefix (again, like some other file managers), you don't have to press anything beforehand. When you get used to it, it's hard to go without it. https://github.com/lxqt/pcmanfm-qt For those preferring lightweight environments, it has far fewer dependencies than dolphin.

I've historically had a lot of problems with Dolphin too. It has gotten a lot better though. Try https://github.com/lxqt/pcmanfm-qt as an alternative. It feels native in Plasma/Breeze and is more traditional. I like it.

KIO is pretty fast I think. Dolphin is insanely fast at least - if you list a large directory almost everything that can't be loaded instantly is loaded asynchronously and streamed in to the UI after the UI becomes responsive. I think the KDE file picker is using other code altogether, I'm not sure why it's so much slower. GIO is horribly slow and makes everything that uses it next to useless, eg [1] [1] https://github.com/lxqt/pcmanfm-qt/issues/462