How will I use NextDNS in the (near) future?

A few days ago I saw that test.nextdns.io no longer works on LG webos TV. That was strange as it was fine just a couple of days before. It said that the is something wrong with security certificate. Ping.nextdns.io wasn't working, but that was not shocking as the browser is a stupid old dumbed down version of Chrome.

Yesterday I tried to change DoH to DoT in AdGuard and it said "No connection". Hmm, I changed to another provider, is working. I try again DoT, nope. I tried to connect to DoH, no longer works. F... I tried to connect in Brave with my configuration, nope. I try the default one, it works. I tried to change networks, Wi-Fi, data, restart phone, router, reinstall AdGuard, new configuration, nope. Everything else is working but not NextDNS, except v4 and v6. I was contemplating to reset the phone as it seems like virus, Brave said something about DNS_probe...
I installed NextDNS app, nope. I installed the NextDNS certificate, nothing.
Today, from what I understand, there was a change in security certificate and that for the moment I can use dns2. I tried to add 2 to the links and is working, for now. I understand even this will stop working in few months.
I have basic knowledge and understanding of this field, so what can be done in connection with the security changes NextDNS made? Is there something the user can do?
I understand progress and changes but it can't be done over night if even relatively new devices can't be used... Maybe the change can be done in 1 or 2 dns and let one for older or more basic devices? I don't know...
You have users from all over the world, not all afford to buy new devices and many vendors do not provide updates to the os, if this depends on os updates...
In the name of progress and security more people will be forced to use unencrypted v4 and v6 if they still want to use NextDNS?

So for now you can use this format:

https://dns2.nextdns.io/YourID

tls://YourID.dns2.nextdns.io

*If you can edit the links, even the NextDNS app does not allow you to set up the link and did not tried to connect to dns2.