The Slack bot that Jira's integration creates is supposed to be able to recognize issue numbers and render previews in Slack channels as advertised here:
https://slack.atlassian.io/
It's not working, which we have reported. The Jira support team has created a support case for this, linked below. Unfortunately it's a low priority for them. If you use the Slack integration and value this feature as we do, I encourage you to view the link below and vote for a resolution.
https://jira.atlassian.com/browse/JRACLOUD-68935
