Looks like you ticked “experimental features” when installing. This is what the next version of HACS will be like.
By default the start view shows the HACS integrations you have already loaded. If you have only just installed it, this will only be HACS itself. To see all the available integrations and cards, click on “clear”, top right.
I’ve been using the new UI for weeks now. Everything works just fine, including adding custom repo’s. Use the filters top right to pick what you want to see, search for what you need, click on it to see details and install.