Could my ISP be blocking turris.cz domain

Good day

I’m new to this forum and I’ve recently bought a Turris Omnia 2020.
Since day one on 3-Jan-2021 that I’m connected using the Omnia, I see high latency to internet compared to my retired Linksys WRT1200AC running OpenWRT 19.07.5 and as of today I cannot connect to anything on turris.cz domain.
The internet is unbearably slow. I’m running TOS5.1.4 HBS and I was notified via e-mail of a failed update. The same info I saw on the Notifications on reForis.

Is there any workaround?

Sounds like some DNS problem. You could check that latency on IP layer is OK by ping 1.1.1.1 on any machine or the router (or 8* or 9* from those that are easy to remember).

Default is forwarding with DNSSEC validation to ISP’s DNS resolvers, I think. The first easy thing you can try is to disable forwarding or choose some other target resolvers. It’s in the (re)Foris GUIs in DNS tab.