Tried both additions to .htaccess and still broken.
I tried that, didn’t work.
I now think the problem is that my homepage keeps trying to point to http://www.domain.com/wp-admin, but when I copy and paste the address without the http://www., it works and I can access the dashboard as usual. Any links to the dashboard from the front end, however, try to use www. and it fails, redirecting me to the homepage.