If you have no outward supplies but have inward supplies for July 2023, you should file a nil GSTR-1. For your GSTR-3B, you need to report your inward supplies and check GSTR-2B, rather than filing it as a nil return. GSTR-2A is auto-generated and doesn't require manual filing.
29 July 2023
No outward supply then file GSTR 1 return as NIL...
Have inward supply then file GSTR 3B return based on Your inward supplies and Check GSTR 2b also...
Don't file GSTR 3B as NIL return...
28 October 2026
With no sales you still file GSTR-3B normally and claim the ITC in Table 4 (it stays in the ledger for future use); 'Nil' filing (including by SMS) is meant only when there is no outward supply, no inward supply/RCM and no ITC to claim; GSTR-2A/2B are auto-generated and need no filing.