Some great apps have already been mentioned here so I’ll share a last resort if you need: GMaps WV (Google Maps WebView Wrapper). It’s Google maps in a restricted sandbox made by the Divest OS dev and app is on FDroid.
When I used it on a more regular basis a year ago it didn’t have ads and after installing it just now to test and share this, I haven’t found any either.
Privacy wise it’s not as good as omsand~ or Open Street map but you could use it on another profile in your phone if you have android if that is a concern.