The issue with Apps Script having an error when a user is logged into multiple Google accounts has been a problem for a long time.
There are multiple open bug reports related to authorization errors when a user is logged into multiple Google accounts.
For example:
That issue has been open since
Nov 13, 2017
So, for the error that you are getting when users are logged into multiple Google accounts,
I don't think that there is a workaround.
Because the installation fails completely, there is no opportunity to warn the user to do something else.
You'd need to warn people in the Marketplace add-on description to log out of multiple accounts and log back into
just the account that the add-on should be installed with,
and hope that they read it.
If the add-on is already installed,
then the best that you can probably do is to warn people when they install the add-on that being logged into multiple accounts
will cause an error.
Unfortunately, this is a failure of Google to fix a very important issue.
I don't know what the other issue is.
I can only guess. If the failures are only in user accounts inside of domains,
then maybe it's something to do with how the admin of the organization blocked something?