I'm not a Symbiosis user, but I would imagine that your issue is not whether it's Letsencrypt or Comodo et al.
The issue seems to be the update process. Letsencrypt is slightly fussy for its automated updates to work. I imagine however, if you get them to renew automatically, they will be less trouble than a 'professional' certificate that you have to remember to update/install manually.
I use Letsencrypt for ~ a dozen domains, and they all update automatically just fine. The difference is that I use plain Debian, and have to do a one off configuration of each domains config file. It's pretty much a copy and paste though.
Not wishing to go off topic, but for those wanting the latest Debian and Symbiosis, you could try Debian + Virtualmin instead. It's what I've used for many years, and it mainly works just fine. You get easy domain managment on a plain Debian (or whatever).