What I propose is to change your way of taking photos.
Place your keyboard on the table. Take the photos from the top. Then go around the table and take the photos of the sides. Flip the keyboard and repeat the process.
Create two chunks in metashape. Align them separately. Create low poly mesh and cut it just 1 mm above the table. In photo panel import mask and as a source use a mesh. You can place all photos in one chunk or you can align chunks by points. In align panel use "apply mask to key points". It should work. If not create two models with desired resolution and register then in external software. You can do it on the point cloud level or mesh. It depends on you.
If you want to do it in one chunk: put everything together in one chunk. Create a few masks. Use "apply the mask to the tie points" and align the model.
If overlaps between the bottom and top of the keyboard are not enough to align photos properly, place your keyboard horizontally and use the first method I mentioned. You can build for example a Lego holder. This will work for sure.
Good luck