Thanks for using our Cisco Community. For this type of migration I strongly recommend to follow this guide:
Migrating ASA to Firepower Threat Defense Site-to-Site VPN Using IKEv2 with Certificates
Thanks for contacting our Cisco Community. I'm not sure about what type of Site-to-site you have, if it's with certificates, IKEv1 or IKEv2. Nevertheless here is some helpful information that you can use to migrate this type of configura...
Thanks for using our Cisco Community. Yes, as of now, both procedures are supported but as you mentioned the Migration tool is the best practice to migrate ASA to FTD.
Muchas gracias por la oportunidad. Te comparto información al respecto:
ASA multi-context to FTD multi-instance:
Espero que todo vaya excelente. Te comparto las recomendaciones con respecto a software para migrar de ASA a FTD: