Hi,
You are welcome! It might be actually possible, using a custom code. I have constructed a possible solution, I am not sure if it works correctly in every case, it does on my test environment, so worth a try.
1. Make sure to delete the previously suggested filters, and make a single checkbox filter with this exact configuration: https://i.imgur.com/xQFHRI1.png
The Custom field and the Type and the Value fields are important, the rest does not matter in this case.
2. Add this custom code to the functions.php in your theme/child theme directory (copy from line 3 only!). Before editing, please make sure to have a full site back-up just in case!
This code will detect this filter and transform it to a date filter instead – depending on the checkbox state.
After that, save the options, and try it. If I am not mistaken, then this should likely work.