Google Photos: How to share photos with a link, and not get a 404 error

There are several ways to share photos using Google Photos.

1. Direct sharing with other Google Photos users
2. Mobile only: Share to ... an app (this copies photo(s) and opens them up in the designated app. 
3. Copy Link

How to share with a link, and make sure it's the right link

When I need to share with someone who doesn't use Google Photos, I like to use the share with link technique. I copy the link from Google Photos, then I paste it wherever my recipient is sure to see it, an email addressed to them, a text message, a Facebook post etc. Anyone who has the link can see the picture(s) represented by that link.

As long as it's the right link! You need to follow the proper steps, not just grab a link with the right-click/copy link method, or copying from the address bar. If you do grab the link with either of those two generic methods it will start with Photos.Google.com/photo/.... That is a link to your photo library and only you will be able to see it. Anyone you send it to will just see a 404:that's an error. The correct link should start with photos.app.goo.gl/...
Here's how you get the right link:

Google Photos updates in 2019: Faster, Better, Changes, and New Features

Google is changing and improving Google Photos all the time. Since the 2d edition of the book was published in June of 2018, I have been keeping a list of all the changes.

You are updating your Google Photos app aren't you? 

If you're not sure, here's a video on How to Update Google Photos.

Here are my picks for the most significant recent updates.