I recently wrote a blog to help teams decide between writing the SDKs for their APIs by hand or generating them using a code generator: https://www.apimatic.io/blog/2021/09/the-great-sdk-battle-bu...
TLDR: There are a good many technical challenges to creating high-quality SDKs in multiple languages for a medium to large-sized REST API and most teams seem to underestimate the amount of effort required to build and maintain SDKs. The speed and savings from code generation is quite compelling and a modern commercial code generator like APIMatic has a wide-enough feature-set that most REST APIs don't require writing SDKs by hand anymore.
Disclaimer: I am a contributor to APIMatic Code Generator.
Swagger Codegen: https://github.com/swagger-api/swagger-codegen
OpenAPI Generator: https://github.com/OpenAPITools/openapi-generator
AutoRest: https://github.com/Azure/AutoRest
NSwag: https://github.com/RicoSuter/NSwag
oapi-codegen: https://github.com/deepmap/oapi-codegen
go-swagger: https://github.com/go-swagger/go-swagger