I tried most of these and settled on a something that is offline, non-electron and fast enough: QOwnNotes (https://www.qownnotes.org/)

Some highlights:

1. markdown support (with preview)

2. plain text editing

3. hierarchical notes

4. keyboard accessibility

5. decent plugins (plantuml integration among others)

6. note folders (separate workspaces)

7. responsive dev team

8. nextcloud integration