I use Lightroom Classic and have no interest in Lightroom or Behance.
Can Portfolio be used with Lightroom Classic and Creative Cloud only?
Yes, because you can upload photos manually if you want. You don't need Cloudy Lightroom or Behance.
The easiest and best way to use Portfolio from Classic Lightroom is by "syncing" collections of photos to Adobe's server. In Portfolio, you can then set up "integrations" with these collections, ie pointing Portfolio pages to the collections on Adobe's server. If you then change photos in Classic, you can refresh those integrations (Adobe use "reset" to mean refresh).
John, in relation to "Yes, because you can upload photos manually if you want.". I have yet to figure out how to use just LrC with Portfolio. The Integrations listed are Behance, Adobe Lightroom and Adobe Stock. When I looked up Portfolio Integrations, there does seem to be any link to LrC. In relation to the OP's question of "Can Portfolio be used with Lightroom Classic and Creative Cloud only". Can you elaborate on how to move photos to/from LrC and Portfolio? Thanks.
You can Sync a local Collection, so it presents as an Album in the cloud. This may be branded as "Lightroom" in the web but you can do this all using only LR Classic.
You can then add a photo gallery page inside your Portfolio site. You can tell Portfolio to fetch the content for this gallery page. from that Album within Creative Cloud. As you further edit the photos within LR Classic, and change membership of this Collection there, those changes sync out to the Album. When desired you can tell Portfolio to discard the previously fetched content of this gallery page, and fetch replacement content from the same Album as before. You have to actively tell it to do that, it does not happen live. And that's arguably no bad thing, because IMO a public portfolio type site is best when it's consciously curated and updated.
If instead you want to show someone a dynamically changing photo gallery, immediately reflecting your work done locally, you can instead share a live link to that Album where it sits within Creative Cloud. That can be viewed directly.
There's a great danger of making this seem harder than it is. As I wrote before, in Classic Lightroom you should sync some Collections. These are then shown in Portfolio when you go into Integrations.
So in Classic Lightroom, create a new Collection of photos and set it to sync. Wait for sync to complete, then go to your Portfolio site and click Integrations. Add Album lists all your synced Collections. You just select one or more, click Import Selected, and they become pages in your site.
If you change photos in the collection, you need to go into Portfolio, go to the page and look for "reset from Lightroom".
Just try it - it's pretty easy if you follow these steps.
Thanks Richard and John. I didn't realize the 'album' construct was outside of Lightroom Cloudy. Makes perfect sense now. LrC Collectiom -> Creative Cloud Album.