QOwnNotes (very regularly updated) & Joplin are must haves as far as markdown + private sync (dropbox (free) account, etc) are concerned.

NoteCase pro can set up complex personal servers easily, must have too, best overall outliner, multi platform.

For HTML linking of files as outliner editing, Windows only, try Pro version, probably second best after NoteCase Pro but good at linking html files:

https://www.bauerapps.com/rightnote-version-comparisons/