Testnet fast catchup stuck at processing accounts

[fabrice]

Thanks for coming back with the solution!

Yes, some Internet providers are blocking some DNS queries indeed.
In particular, they are blocking DNSSec that we use.
A non-ideal workaround is to disable DNSSec:

DNS problem with Algorand Server on Ubuntu 20.04

is not normal. Are you on your personal network or a company network with some firewall/proxy? Can you try to disable DNSSec? Option DNSSecurityFlags in config.json (https://developer.algorand.org/docs/reference/node/config/) Concretely, update the file $ALGORAND_DATA/config.json (assuming $ALGORAND_DATA is your data directory with the file genesis.json) so that it looks like: { "DNSSecurityFlags": 0, ... }