We have been using a GoDaddy cert for the past several years for our PBXes with relatively good success (Yealink seems to randomly not like certs, but that is another story). This GoDaddy cert will soon expire. We are considering moving from a paid GoDaddy cert to a Lets Encrypt cert. If you use LetsEncrypt with FreePBX please provide feedback. Our biggest areas of concern are: Yealink phones accepting LetsEncrypt certs (T4X and T5X phones), auto renewal of certs without any user intervention, ease of use and maintenance, etc.
We have many client PBXes and I do not want to make a switch and regret that switch.