I'm happy the "outliner" (tree style notes) space is growing.
While I knew about #Workflowy, #Dynalist, #Roam, #Transno (all proprietary), #Logseq (FOSS, but doesn't save collapsed state), today I found out about Athens research, which puts an emphasis on privacy, independence and using a real graph structure and looks super promising (besides indentation being slow so far).