this exists, its called OWA (open web auth) (https://magicsignon.org/page/openwebauth/fep) and is implemented in hubzilla and other softwares of the family.
oldmonq
joined 1 year ago
this portable identity feature has existed for a number of years in hubzilla, its implemented as its own 'zot' protocol, offering nomadic identity as well as account cloning(redundancy).
hubzilla has private forum/group feature.