Miro, Excalidraw, tldraw, OpenBoard Whiteboard, Whiteboard Team, Coccinella, Groupboard, NoteBookCast, Witeboard, Conceptboard, Scribblar, CoSketch, Twiddla, IPEVO Whiteboard, Limnu, WebBoard, Scriblink, WrittenUp, skrbl, drawonthe.net, PrimaryPaint, Board800 are some alternatives to IDroo.