See https://github.com/jumbojett/OpenID-Connect-PHP/issues/190. The best solution would be to add support for specifying parameters to the well known configuration in the extension config.
$wgPluggableAuth_Config[] = [
'plugin' => 'OpenIDConnect',
'data' => [
'providerURL' => 'https://login.microsoftonline.com/[tenantID]/v2.0/',
'clientID' => '[Application (Client) ID]',
'clientsecret' => '[Secret from Certs and Secrets]',
'wellKnownConfigParameters' => [
'appid' => '[Application (Client) ID]'
]
]
];