The GNU GPL doesn't solve the problem for software that isn't licensed under the GNU GPL.

True, but licensing the software under the GPL does provide for "right to repair".

If your plan is to change copyright law, then just require all software be GPL licensed.

The GPL goes further than just the right of an individual to repair software on their device or that they use online.

the GPL is not the only solution to this problem

GPL does not prevent a company from architecting their system to use an online component such that you wouldn’t have any practical right to repair the system as a whole.

AGPL does, though.

FOSS licenses are the equivalent of some hardware manufacturers voluntarily allowing repair. OP is asking for an equivalent of a guaranteed right to repair from all manufacturers.

Well you can do that by mandating by law that all software (including the one only provided as an online service) have to be released on a FOSS license.

Now how do we force vendors to use it?