I have not been able to get network.trr.mode 3 working since the last FF update to version 76. My settings are as follows:
network.trr.mode = 3
network.trr.custom_uri = https://mozilla.cloudflare-dns.com/dns-query
network.trr.bootstrapAddress - 22.214.171.124
same setting as i have always had working NP but version 76 will not allow trr mode 3. I even did a complete OS rebuild with FF 76 with these settings and it still does not work. Only trr mode 2 will work and Cloudflare ESNI checking tool confirmes nothing is working.
Is there some new requirement for FF ver 76 to get mode ‘3’ working?