I get this error right after a reboot of the system. This seems to be a timing issue, as if it tries to download the blocklist before DNS is fully operational, or perhaps before networking is fully up. When I force a new attempt to download after the reboot has completed, then it loads without issues.
2023-04-29T18:35:43 Notice unbound blocklist: https://raw.githubusercontent.com/hagezi/dns-blocklists/main/domains/multi.txt (exclude: 0 block: 0)
2023-04-29T18:35:43 Notice unbound blocklist download: 0 total lines downloaded for https://raw.githubusercontent.com/hagezi/dns-blocklists/main/domains/multi.txt
2023-04-29T18:35:43 Error unbound blocklist download : unable to download file from https://raw.githubusercontent.com/hagezi/dns-blocklists/main/domains/multi.txt (error : HTTPSConnectionPool(host='raw.githubusercontent.com', port=443): Max retries exceeded with url: /hagezi/dns-blocklists/main/domains/multi.txt (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x8027cf910>: Failed to establish a new connection: [Errno 8] Name does not resolve')))
2023-04-29T18:35:43 Notice unbound blocklist download : exclude domains matching ^(?![a-zA-Z_\d]).*|.*localhost$
https://github.com/opnsense/core/issues/6523
Yes, that's it, thanks.