Hello, I'am new here. My name is Marcin Kuczera and I work for local telco (leon.pl) in southern Poland (Rybnik and surroundings) (near Ostrava).
We used to have lot of problems with our OLT vendor (Ericsson then Calix) so we were enforced to find solution so... finaly we do own ONTs (as LeoLabs, an R&D branch of Leon.pl).
It is totally independent of fibrain and based on different chipsets (we use Realtek). Local software development and bug fixing.
If you have any questions, just ask, we can help as we are also an ISP with much better problem understanding than just a vendor.