Please don't flag this question as a duplicate because I really need your help. I once used OpenDNS in my router to block some websites & now I'm stuck with at whatever I do. I have already removed OpenDNS from my router & tried half of the commands suggested in other question but none of them work for me. Most of the websites which deal with a proxy, adult content etc. are all blocked & I'm requesting for a solution.
This should clear it
# sudo systemd-resolve --flush-cache
You can check with
# sudo systemd-resolve --statistics
it should show 0 in Current cache size
DNSSEC supported by current servers: no Transactions Current Transactions: 0 Total Transactions: 93750 Cache Current Cache Size: 0 Cache Hits: 18686 Cache Misses: 28576 DNSSEC Verdicts Secure: 0 Insecure: 0 Bogus: 0 Indeterminate: 0
Maybe this version also has two (2) DNS caches, like Ubuntu 20.10.
Please check the full tutorial to flush DNS caches: