Details related to "CA signature digest algorithm too weak"

Hi all, having query related to error log "CA signature digest algorithm too weak" ..

this is shown after I migrated from openssl 1.1.1u to openssl 3.1.1

the same goes off .. when I set SSL_CTX_set_cipher_list(ctx,"ALL:eNULL:@SECLEVEL=0");

any idea related to this.