Is it possible to create websites for other people in Adobe Portfolio?

yes.

Portfolio does not have a forum here for support... these links may help
Technical support: https://help.myportfolio.com/hc/requests/new?ticket_form_id=177168
Faq: https://help.myportfolio.com/hc/en-us
Getting Started: https://helpx.adobe.com/creative-cloud/how-to/create-portfolio-website.html
Choose a Theme: https://portfolio.adobe.com/themes
Theme Features: https://help.myportfolio.com/hc/articles/360035995733-Themes-features
Migrate to a new page: https://help.myportfolio.com/hc/en-us/articles/10872890414235-Migrate-Adobe-Portfolio-sites-to-another-account-Overview
Lighrtroom Integrations
https://blogs.adobe.com/jkost/tag/portfolio
https://lightroomkillertips.com/getting-images-lightroom-adobe-portfolio-just-got-lot-easier/
https://digital-photography-school.com/create-beautiful-online-gallery-lightroom-classic-cc-adobe-portfolio-15-minutes/
Custom Domain
https://help.myportfolio.com/hc/en-us/articles/216489627-Manually-configuring-a-custom-domain
https://help.myportfolio.com/hc/en-us/articles/209448927-Using-a-custom-domain-with-Adobe-Portfolio