I used to work with the plugin ProfileFromPoints, but it is not avaible 8or updated) in Qgis 3.
I wonder if there is another one which does the same or if there is an easy (foolproof) way to use the same plugin in Qgis 3.
TlugProcessing plugin will do the job. You can find it in processing toolbox after instalation.
The Profile tool can also sample points, however at least for me it is quite slow. A big plus going for it is that it is interactive - if you move your mouse on the profile, the position will be shown on the map. To get around the slow display from points, I create a grid from the SAGA toolset and then use that grid instead of the points.