Inbox by Gmail is going the way of the dodo, and there's nothing we can do about it. I'm still incredibly bitter about this, but it's time to suck it up and work out how to make Gmail function in exactly the same way (or as close as possible). "Save to Inbox" was one of many handy features, but it's already been removed from the Android app and the Chrome extension has also vanished. Thankfully, InboxIt is here to reinstate it, on mobile at least.
The alternative right now is simply to send an email to yourself. InboxIt essentially does this for you, removing some of the tedium from the process. Simply tap the InboxIt icon in the Chrome sharing menu or wherever else you're sharing from, and it will automatically email the link to the account you set up.
As well as sending yourself links, you can also use the app to add reminders to your inbox, which is another feature we'll be missing when Inbox goes away completely. There's an app shortcut to make this easy to access, so if you've gotten used to having reminders mixed in with emails, this could be a good alternative.
Left: The basic reminder interface. Right: A reminder followed by two saved links.
Additional features such as changing the email subject and automatically applying a Gmail label can be purchased for $0.99/£0.99, although I've found the default settings to be good enough for my use.
InboxIt has only positive reviews on the Play Store so far, so let's hope the dev continues to build on this good start.