Office365 Business Essentials email setup question.

I’m not getting clear confident answer on this from Microsoft sales.
Since the connected accounts feature has been removed from Outlook on the web, can users still add their business domain email accounts, gmail, and or hotmail/live accounts? Are there Aliases? Adding domains?

I currently have an Outlook.com account with multiple connected accounts but need the 1TB OneDrive and more.

I assume you're asking about the Outlook desktop app, looking to use that for your needs?

I have 365 Home, so not BE. I use Outlook desktop for 3 accounts: Gmail, Outlook.com and an address on my business domain.

When I used to use aliases like Sales@, Support@ etc, I set them up as addresses at my web host and set them up as normal in Outlook. You can have each of them with their own set of folders in Outlook—Inbox, Sent etc—or you can have them all come into one set of folders.

You can 'reply as' to any email with the account name of your choice—eg someone sends to sales@, you can reply from support@ if you prefer.
Note however that I haven't needed aliases for the last 6 years, so I have no recent experience of 365 changes in that area.

I'm not clear what you mean with "Adding domains". 6+ years ago I had 2 main business domains, I used Outlook for both—so there's no problem handling email accounts & aliases from multiple domains, if that's what you mean.