I ran npx create-strapi-app@beta Strapi5Project --quickstart as you suggested and I went on until npm run develop phase. There it throwed and error which I fixed by issuing npm i ajv-draft-04. Then I tried again npm run develop that ended like the current (non beta) Strapi, that’s to say no browser gets fired and admin url is not available.
The only positive thing is that admin build time is a magnitude faster.