Since #3090 compiling netcdf when S3 switches are enabled fails for both:
autotools: ./configure --enable-s3 --enable-nczarr (uses aws-sdk-cpp)
cmake: cmake ../ -DNETCDF_ENABLE_NCZARR=ON -DNETCDF_ENABLE_S3_INTERNAL=ON (uses internal s3 implementation)
These are the sort of errors one immediately gets:

nch5s3comms.c:95:10: fatal error: netcdf_vutils.h: No such file or directory
   95 | #include "netcdf_vutils.h"

zmap_s3sdk.c:264:24: error: too many arguments to function ‘NC_s3sdkclose’
  264 |     if(s3client) {stat=NC_s3sdkclose(s3client,&info,1,NULL);}

zmap_s3sdk.c:410:9: error: too many arguments to function ‘NC_s3sdkclose’
  410 |         NC_s3sdkclose(z3map->s3client, &z3map->s3, deleteit, &z3map->errmsg);

I created #3122 hoping to fix the problem but also enable these builds on github actions. IMO this build variant should be exercised as well.