Possible, put probably not. See what I say below, though.
If you didn’t know, Cloudflare’s Edge certificates are valid for 90 days as well, but they have an auto-renewing service, so you just don’t notice. However, the only way to access this is by adding your site to Cloudflare (by using their nameservers) so they can have control over the Edge SSL/TLS certificate for your domain. And sometimes, Cloudflare doesn’t even issue the certificates themselves! They also use GTS and Let’s Encrypt!
So overall, you can choose one of two things:
- Get a Self-Signed cert from us and install it, and then use Cloudflare (only with custom domain, though) and let them manager your Edge certificate … or …
- Get a new certificate every 90 days from GoGetSSL, ZeroSSL or Let’s Encrypt (custom domain only) and use our nameservers or a free subdomain. Also with this method, we send an email 30 days from your certificate’s expiry and again 7 days from the certificate’s expiry.
You can choose which is better for you. But know that any route you go, your certificate will only last for 90 days (unless you purchase a certificate, then you have the option for one-year validity).
(“Edge Certificate” means which certificate the browser gets sent, read more: Edge certificates · Cloudflare SSL/TLS docs)