Configuring preferences and options in Outlook.com
I don't know if I fixed my problem or someone at Microsoft support fixed something, but this is what I did and it started working again...
On my android (version 9) phone, went to the Play Store, found the Gmail app and selected "Uninstall all updates" to it, reverting it back to the original factory installation. You might also be able to do this under Settings > Apps & notifications > Gmail.
Then, Settings > Accounts, select the old hotmail account and then remove it.
Then, Settings > Accounts > Add account > Exchange, typed hotmail account email address, then "Manual Setup".
When asked what type of account is this, select Exchange. Enter password > Next, and on "Incoming server settings" changed the server name from imap-mail.outlook.com to eas.outlook.com (from previous notes I made). A new screen then asked for all kinds of remote-control permissions (even a phone factory reset), but once I clicked OK the account was set up and everything synced properly again --email, contacts and calendar. The account shows up (under android Settings > Accounts) as "******@hotmail.com" as type "Exchange".
I don't think I'll let the Gmail app update itself again for quite awhile!