Hello,

Make sure you've technical access rights.

Then from Settings->Technical->Automation->Automated Action. Create new one

* Enter the rule name

* Related Document Model: pick yours e.g Project Issue

* When to Run: e.g. On Creation

* If you've a filter defined you can choose it, or make a new filter, or leave it.

* Then from the Actions tab, in the Add Followers field choose your followers.

* Save

I hope it'll helps

Regards,

Just define that follower on the project. So for all new issue, he will automatically become a follower. In Odoo by default project followers become follower of issue.

Note. It doesn't update the existing issue. To do that probably you have to create server/automated action which will do for you.