That will not work. Some ISP do DNS transparent proxy (forward all udp packet 53 to their own DNS server). You need DNSCrypt or VPN.
It depends how the block is implemented. If it's done by intercepting DNS requests, it doesn't matter what server you _try_ to reach. There's also the Virgin (UK) approach of allowing the correct DNS response, but tampering with HTTP requests (though switching to DNS-over-HTTPS wouldn't help in that case).
Or Quad9, but this could be intercepted.
apt-get install unbound
I was already using 1.1.1.1, did not unblock. Would be very curious if the ISPs were actually proxying my DNS requests. Any tips on how I might test that on Ubuntu?
They generally inspect DNS packets and block hostnames from resolving correctly. Does not matter the destination.