I have had and used lightroom 6 on my I Mac for several years now but my mac just died. I have just purchased the latest mac and was told my LR 6 will not work on it. I backed up my old computer about a week before it died so I have all my old photos etc. Should I be able to import all my old stuff when I sign up for the subscription model of LR on my new computer. I am a total ludite so any answers may need to be aimed at a 5 year old.
PS, on my new mac I would like to have all my photos, libraries etc on a external HD.
My suggestion would be to put all of your photos on an external hard drive, but put the Lightroom catalog and associated files on your Mac hard drive. After you install Lightroom Classic and start the program you will be prompted to upgrade the catalog. Allow that to be done. The next thing that is going to happen is that after the catalog is upgraded You are going to be notified that all the images are missing. This is because they are not in the same place they were on the old computer. In the library module, left hand column, you can right-click on folders and choose the option to find missing folders. This will enable you to show Lightroom where the images are now located. If all of your images are organized within one master folder, you only have to point Lightroom to the location of the master folder. If there isn't a master folder then you'll have to do it a few more times.