Hi Laurag37590452,
As you have mentioned you would like to install and use Adobe Lightroom on your Mac machine however you get an error that it is not compatible.
This is because Lightroom Classic CC and Lightroom CC both are not compatible with this version of Mac OS.
To install and run Lightroom Classic CC and Lightroom CC on your machine you'll need minimum of Mac OS 10.11 (El Capitan), for more information see: Lightroom Classic CC system requirements, Adobe Photoshop Lightroom CC system requirements
So I would recommend you to update the operating system of your machine and then install the the version of Lightroom you need,
Let us know if this helps.