My Photo Stream Shutting Down

My Photo Stream was never a storage service. It would only store up to 1,000 photos and only for 30 days. It was one way that you could import recent photos to other devices. See: My Photo Stream - Apple Support

The first 5GB of iCloud storage is free.

If you don't want to use iCloud Photos, you can still import photos from an iPhone or iPad to a Mac or Windows computer. See: Transfer photos and videos from your iPhone or iPad to your Mac or PC - Apple Support

and you can use Time Machine and/or 3rd party software to backup a Mac computer to an external drive.

You can also use AirDrop to transfer photos between devices.

For what I was referring to, see the following from My Photo Stream - Apple Support

How many photos can My Photo Stream store?

To save storage space, your iPhone, iPad, and iPod touch keep your most recent 1000 photos in the My Photo Stream album. 

First of all, you can include photos in your back up. That’s the way it’s always been. Photo Stream never was a backup for photos.

Even though Photo Stream is shutting down, you will still have the photos from the Photo Stream on the device on which the photos were taken. You will not lose any photos at all.

Copied from the link above…

The photos in My Photo Stream are already stored on at least one of your devices, so as long as you have the device with your originals, you won’t lose any photos as part of this process. If a photo you want isn't already in your library on a particular iPhone, iPad, or Mac, make sure that you save it to your library on that device. 

I have never used a photo storage service but look at Google Photos and DropBox.