[jipy9]

I used StartSSL class 1 certificate for my app (unherd.co). Its free and valid for one year. Here is a good guide that might be of help - https://konklone.com/post/switch-to-https-now-for-free?hn

[akg_67]

I also used StartSSL class 1 for my site (peercube.com) and will highly recommend the help link you provided for getting and installing the certificate.

[OWaz]

I used the same certificate from StartSSL and got an A- grade from SSL Labs.