Does anyone know how I can expose and associate existing jira tickets from other projects to a customer/organization in service desk? More specially, I would like to give them access to read/write to the tickets with a particular epic link in another project within Jira.
Welcome to Atlassian Community!
To allow a customer to view and comment on a Jira Software ticket, it will require a license, otherwise, it will be necessary to open the project to the public (anonymous access) and everyone on the internet will be able to find the tickets.
Note that anonymous access is available only for Classic projects.
If you have any other questions regarding this matter, please let us know.