I’ve migrated from gitlab to github in 2021 which had some issues: https://github.com/piceaTech/node-gitlab-2-github/issues/99

Most important was maintaining the history, so that included:

• user mapping
• commit mapping
• project mapping
• attachments
• issue information
• descriptions, labels, milestones, merge requests

Tool used: https://github.com/piceaTech/node-gitlab-2-github

Have fun.