For optical images you want Sentinel-2 (EU) with 10m Resolution or Landsat 8 (NASA) with 30 m resolution. You can use the Copernicus Open Data Hub and the The USGS earth explorer for download, they offer graphic inferfaces where one can select an area of interest or upload shapefiles.

There are many more data sources, specialized software and/or APIs for Python for batch downloading etc.

When you have downloaded the data, you can use different programs for visualizing and georeferencing the images such as QGIS.

Keep in mind the work with satellite remote sensing data is not trivial and usually requires many postprocessing steps. If you just want to explore the earth surface I would recommend to look for local ortho images from aerial photography. Depending on where you live, this data will be made available for download and/or exploration via a web mapping service (WMS). It is much more detailed and may be more interesting you, and a bit less complicated than satellite data.

Just to be complete as you asked for satellite data in general: Of course there is much more available than just RGB channels. You can get more band e.g. Near Infrared from Sentinel-2, or cool stuff like RADAR from Sentinel-1, LIDAR from GEDI etc. There are plenty of satellite missions for all your desires.

For anyone who wants to dive more into these topics, search for satellite remote sensing. You can also find many tutorials for processing this data e.g. using Python or R.

Awesome question. I don’t have an answer, but maybe try LandSat? It’s NASA. Between general map enthusiasts and geocaching and who knows how many other geographical hobbiests out there, there’s got to be something open source.

Sentinel data from Copernicus is free and of better spatial resolution than Landsat.