It seems that the issue has a different root cause related to a huge blocklist (200k entries in format address=/010sec.com/0.0.0.0 ). With version dnsmasq-2.76-17.el7_9.3.x86_64
everything works correctly with startup time close to zero, with version dnsmasq-2.79-33.el8_10.x86_64 the issue appears.
Googling on topic I notice that dnsmask version 2.90 should solve the issue but is not available neither in repository of version 9.