One of the well-known multiple satellite imagery providing platform is USGS Earth Explorer (https://earthexplorer.usgs.gov/). You can even search and download Sentinel-2 Data Collection using USGS Earth Explorer among with the Landsat Data Collection and many more.

Beside this, please check https://gisgeography.com/free-satellite-imagery-data-list/ website for a list of newly updated free satellite imagery sources.

For free Landsat/SRTM image: http://earthexplorer.usgs.gov

For free Santinel 10 meter image: https://scihub.copernicus.eu

For ALOS global DEM data: http://www.eorc.jaxa.jp/ALOS/en/aw3d30/

Dear there are a hug number of sites provide you free data such as

https://earthexplorer.usgs.gov/

http://www.eorc.jaxa.jp/ALOS/en/aw3d30/

and other

My best regards