Does anyone know how to download lightroom 6 without a cd

Pro Design Tools still have download links. Note that you need to be logged-in to a browser window with your Adobe ID before commencing download otherwise access will be denied.

N.B Its impossible to install on Mac OS Catalina.

https://prodesigntools.com/adobe-lightroom-6-cc-direct-download-links.html

Do you have buy a license and have a serial number?

You may download ONLY if you bought direct from Adobe via download
-Log-in to your account and click this link https://account.adobe.com/products
--click Order history on the left and then the link to your order that will show on the right
--and finally click the link "Downloads and serial numbers" that will appear
--as always, write the serial number in a text file AND copy that text file and the
---download file(s) to an external drive (or two) to be sure you have what you need
-if you did not buy direct from Adobe via download you must find your original install
--if you have an Education or volume license you MUST use your original media
--the link for an Education or volume license download is not available at all
-if you bought a disc and don't have a drive you will need to buy an external USB drive
-if you bought a download from a 3rd party vendor you will need to contact that vendor