Whay cannot Keynote be installed with macOS 15

Apple does not keep past full-installer versions of Pages, Numbers, or Keynote for user download. Keynote v12.1 in the Mac App Store requires macOS Big Sur or later for installation.

If you never had installed Keynote from the Mac App Store since Fall 2013, then there is no means to get a version for Catalina. If you did perform that install, then it may be possible for the Mac App Store to install the last compatible version (11.1) of Keynote into Catalina.

Launch the Mac App Store. Sign in with the same Apple ID that you used to install Keynote previously. Press cmd+0 (zero) to open the Purchased panel. If Keynote appears there with a blue cloud outline and down-arrow, click that and Keynote v11.1 should be installed for you on Catalina.

Quit the Mac App Store and reboot your Mac.

If you have Keynote still installed in /Applications, check its version and if it is v11.1, then that is the last compatible version of Keynote that is available for Catalina. If it is earlier than v11.1, then if you have that Keynote backed up to Time Machine, you can move the application to the Trash and empty the Trash.

Now, you launch the Mac App Store and sign in with the same Apple ID that you used to install Keynote previously. Press cmd + 0 (zero) to open the Purchased panel, and see if Keynote now has a blue cloud and down-arrow icon next to it. If so, click that and you should receive a dialog offering to install the last compatible version of Keynote for Catalina.

If you are on that Purchase panel and Keynote does not appear, then you likely installed it previously with a different Apple ID.

Of all the apps i have Keynote is the only one not allowing me to update as there is not a cloud symbol beside it. So how do i proceed with a MacBook which cannot be upgrade beyond Catalina