Per the MS Teams and Jira release page:

Teams needs access to Jira and to do this, it needs an account with permissions to read the Jira Project(s) you want it to communicate with.  To do this:

• Non Saml:
  • Simply create an account on your Jira Instance, give it the rights and note its login information for teams
• SAML Integrated:
  • While not supported by Microsoft, its hackable.
    • Create an account on your Jira Instance, give it the rights and note its login information for teams
    • Turn off/Disable temporarily your SAML Redirection, using local auth only.
    • Use the login with the Jira Teams app to get the OAuth Authentication setup
    • Re-enable SAML Redirection

Please consider fully supporting SSO/SAML/Okta integrations without the need of a workaround.