Trello, Workflowy, CherryTree, Dynalist, OmniOutliner, Org mode, Tkoutline, CrossLine, MyLifeOrganized, Opal, Listography, TreeLine, Nimbus Note, QOwnNotes, OutlineEdit, Checkvist, Visual Outliner, Orgro, Orgzly Revived, Widget-Board, Dashword, GitJournal, Notea, Writing Outliner, CarbonFin Outliner, buzz.opml, Redberry, beorg, Cloud Outliner, Outspline, Cloud Outliner Pro, The Outliner of Giants, Vimflowy, Todo (Rakuishi) are some alternatives to Orgzly.