Id say no. Its not a public beta right now and only is available for genuine, registered developers with an interest in getting their apps to fully support the new system.
You'd have thought that Now would have such registered developers and are working as we speak to ensue that their app is iOS 15 compatible..... but we know from experience that some just leave it and let it go live then their customers complain that its not working and they take an age to fix it when they have had access to the developer beta for months and not bothered to check themselves.
Anyway... assuming you are not a registered developer then forget about it for now.
There will be a public beta starting up in about a months time as there usually is but again they always warn you that it is a beta, is buggy, and you should not really install it on your primary device.