Cloudflare is still using the Alt-Svc HTTP header. Use Ctrl+Shift+J to see the 'Browser Console' which contains logs in the form "Alternate Service Mapping found: https://blog.cloudflare.com:-1 to https://cflaresuje2rb7w2u3w43pn4luxdi6o7oatv6r2zrfb5xvsugj35....

Cloudflare only sends the header to clients it detects as Tor Browser. If you have tweaked your config or are running an older version, it may not detect correctly. Even if it had previously worked.

This technique is not "better than" the "Onion-Location" approach. They complement well. Use the 'Alt-Svc' header for all users with Tor Browser's user agent and send "Onion-Location" to all users. If a user decides to opt for the .onion address, they can. But they don't have to.