Let’s Encrypt root certificate expired (urgent)

It doesn’t really have anything to do with the server.

Provisioning my own SSL/TLS certificate seems a little bit risky for me.

Installing a certificate is actually pretty easy and safe. The only trick is I don’t know if other TLS certificate providers will have the same compatibility issues as Lets Encrypt. Probably the big names (Verisign, Comodo, GoDaddy) will provide certificates with the greatest compatibility. But I haven’t been tracking this issue closely.