QGIS 3 has a lot of new features and new tools for geoprocessing and spatial analysis, however there are some tools from QGIS 2 that hasn´t migrated yet. An example of this break was the OpenLayers plugin, one of the most popular and first plugins in QGIS 2 that is not available in the new version of QGIS.

OpenLayers plugin provide maps from Google, OSM and Bing in QGIS 2. Basemaps in QGIS 3 can be inserted as a XYZ Tiles on a process described on this tutorial. However, QuickMapServices plugin allows the search and implementation from a set of basemaps on different formats (TMS, WMS, WFS and GeoJSON) in QGIS 3.

Some of the basemaps available in QuickMapServices are:

Hybrid Google Satellite Image:

Google Satellite Hybrid

Hybrid Google Hillshade Image:

Google Terrain

Sentinel 2 Cloudless Image:

EOX::Maps - Sentinel-2 cloudless

OpenStreetMap Road Map:

MapSurfer OSM Roads

There is a website where you can have more information about the available basemaps, their extension and perform thematic searches:

http://qms.nextgis.com