Wildcard Subdomain SSL giving SSL error - ERR_SSL_PROTOCOL_ERROR

You can do that, but you will likely want to secure HTTPS for those subdomains first, or people browsing to the site will receive certificate errors before getting redirected.

Since your site label matches any subdomain, you’ll need to use On-Demand TLS or a wildcard certificate. The former has been discussed in the other thread, and if you want to pursue a wildcard certificate, you’ll need to use DNS validation.