Previously I have been using Points2One to make lines from points in QGIS 2.18 but the plugin is not available in QGIS 3.0.
I am wondering if there is an alternative?
I Think Points2One is the easiest way to connect points with lines but this plugin is not adopted QGIS3 yet. U can try this steps in QGIS command panel. It works for me.
To create polygons from points,you can also use
1) "points to path", then
2 ) "lines to polygons"
3 ) "polygons to lines" tools without need to install any plugin.
Hope points2One plugin adopt Qqis3 quickly.