I have done this before, putting them into an EchoMap94. Clean up waypoint names and such and then export them to a. This weekend I'm going to try getting my waypoints out of the 4208 (.adm file) and into Homeport on a PC laptop. Garmin's current software suite of Express, Homeport, MapManager, MapInstall are all there to sell charts. I replaced mine with a 32gb card - doing it now instead of later when its filled up! Only pain is the card slots are on the back of the unit but you can buy extenders to put the slots somewhere else.
My unit has two micro-SD card slots one of which had a 8gb card that is used for extra storage for downloaded maps, Active Captain and Quick Draw. I have been able to transfer my HomePort waypoint sets to and from my 943xsv. The good news is the new units that support Active Captain also have the same Manage Card functions the old units have. HomePort only supports g2 maps which are no longer available. If you want to run HomePort on the MAC you could install Parallels and install an pre-Catalina version of OSX or Windows 10 in a virtual machine. From what I gather HomePort is not going to be updated.
I swapped messages with Gil of SeimperFi on The Hull Truth.