xls to 123 conversion is technically doable, but nowadays of very limited use, unless you need data in old Lotus 1-2-3 format, typically for old machines or just for fun.
The issue nowadays will be in in finding a tool that still supports saving to .123 files, obtaining copy of Lotus 1-2-3 on abandonware websites might be the best solution actually. You just will have to export your Excel sheet to CSV or any format that can be imported to Lotus software.
Various versions of Lotus 1-2-3 can be found for example in the WinWorld abandonware library.
Updated: September 25, 2023