You can authorise an org in sfdx via this command
sfdx force:auth:web:login -r https://customer1customdomain.lightning.force.com -a customer1
When the org is SSO-enabled, I can only login by bypassing SSO by appending ?login to the URL:
https://customer1customdomain.lightning.force.com?login
However, I can't seem to make it authenticate the sfdx connected app.
How do you authorise sfdx in a SSO-enabled org?
https://domainname.my.salesforce.com
. It opens a browser up which authenticates with SSO and says "successfully authorized" in the terminal