Lightroom doesnt seem to offer any older versions

What version of macOS is the 2015 MacBook Pro running?

The Creative Cloud app shows back to version 6.5 for me, for Lightroom (not Lightroom Classic).

My Mac is running macOS 14.7.1.

If you don’t see those, what might be happening is:

• Adobe has a stated policy that you can use the Creative Cloud desktop app to install the last two major versions of an app. Currently, that’s versions 7 and 8. (Sometimes there are exceptions, which is probably why it also offers version 6.5.) 
• To install the oldest available version, your computer must run a version of macOS supported by that app version. 
• At the time a major version is first released, it tends to support the last three versions of macOS. This matches Apple’s own policy of providing updates for only the last three versions of macOS.

Lightroom 6.5 supports macOS version 11 and later.

Lightroom 7 supports macOS 12 and later.

Lightroom 8 supports macOS 13.1 and later.

Does your Mac meet any of those macOS requirements? If it doesn’t, that might be one reason why nothing is available for your Mac to install.