Interesting idea to use GitLab to manage home renovation projects.
It’s a source control system so the primary benefit in using your method is the ability to version files. I could see the benefit of this over other tools if you were using it store plans/schematics for your modifications to the home that you could potentially want to roll back.
In my home, it’s Trello for home improvements but I guess any of these kanban style boards will work. GitHub offers free private repositories so that’s an option too.