If everyone has solar panels on their roof, you can still have the central grid and you can still share power from house-to-house, though.
Generally speaking, decentralized solar refers to a centralized grid that is heavily augmented with decentralized solar, not “truly decentralized” solar.
A redirect isn’t necessary if you control the DNS servers. If you control the DNS servers, you can MITM the website for any visitor because you can prove that you own the domain to a certificate authority and generate a new, trusted HTTPS cert. (Depending on specifics this may or may not foil the anti-phishing capabilities of Passkeys / U2F.)