I'm afraid the Support team doesn't handle the bugs in any way. Please search for a relevant report, and keep an eye on that report for any future updates. ^NS
A username is reserved for 37 days after you change it. This means that once your 30-day cooldown is up, you'll have another 7 days when no one else can take the username. However, you're also welcome to contact us at msft.it/6015ZCfgc so we can look into this for you. ^NS
You may just need to try logging into the Jira site at a later time. Migrating your Mojang account will not have had any effect on your Jira account. ^FF
You can tell us the name that was previously on the account instead. If you're not sure if the email on the account has changed, you can still provide us with the email that it should be connected with. ^FF
Please visit our bug report site to see if the problem has already been reported: msft.it/6013ZCkGf. You can upvote if the issue hasn't been resolved. If you think you've found a new bug, visit our help site here on how to submit a report! msft.it/6014ZCkGA ^FF
Please visit our bug report site to see if the problem has already been reported: msft.it/6018ZCXSq. You can upvote if the issue hasn't been resolved. If you think you've found a new bug, visit our help site here on how to submit a report! msft.it/6019ZCXSS ^FF