Craft 3 multisite - are entries accessible between sites? In multi-site is it possible to access entries between sites in the templates.  Like a feed?   ie. entry "a" on site "A" shows up in an index on site "B", and links back to the entry on site A, not a duplicate of the entry on site "B"?
Yes it is. Just include the site id of the the site in your query

set siteId = 2
set entries = craft.entries.section('foo').site(siteId).all()


if you want to get the current entry for another site

set currentEntrySiteB = craft.entries.id(entry.id).site(2).one()


If you want to search for disabled entries (for example in CP templates) for other sites you can do

craft.entries.id(entry.id).site(2).enabledForSite(false).one()