Today I learned Tuning Gum can turn Link monsters into tuners.

So Tuning Gum’s first effect allows you to turn one monster on your field into a tuner—including a Link monster. It adds a Tuner tag to the monster description, and even turns the Link counter green.

Unfortunately the fun stops there as you can’t use it for synchro summons.

Not sure if it counts for any card effects that requires you to have a tuner on the field.