Well after having spent some time going over the 85 32-bit apps on my MacBook Pro, it is apparent that the vast majority are from Adobe, Apple, Microsoft, and Sony.
Adobe 32-bit files seem to be mostly connected with the older stand-alone apps like Photoshop CS6 and Lightroom 6. I certainly hope my Adobe CC will work correctly if I upgrade to Catalina. Surely Adobe has upgraded everything necessary to work in 64-bit environment. I checked and the PS CS6 app is 64-bit. But another thing to research before deciding on whether to upgrade. I use the CC subscription, but I keep the PS CS6 and LR 6 apps just in case Adobe raises the subscription rates too high.
Apple has quite a few 32-bit apps. I assume those go away and/or get replaced with Catalina. One would hope anyway.
Microsoft has nearly as many 32-bit apps as Adobe, but they are mostly connected to the old Office for Mac 2011 I’ve got installed. That is the latest Office I’ve got. I only use the Excel app, so I need to transition into OpenOffice and Numbers. I’m and old Excel user from way back, so I really don’t want to, but I see no other choice if I upgrade to Catalina. I’ve installed Office for Mac 2011 on my Mac mini running High Sierra so I will still have that capability if I want to use it.
The Sony 32-bit apps are all related to the PlayMemories Home apps that accompany my Sony cameras. I have installed these on my Mac mini now. I rarely use them. Sony posted a notice that basically said they have no intention of EVER releasing them as 64-bit and therefore they are discontinuing them after March 2020. Thanks Sony, you bleeping bleeps! Oh well not really that big of a deal since I rarely use them anyway and there are 3rd party apps that do what they do.
Most of the rest of the 32-bit apps except for Nebulosity 3.x were apps I rarely used and don’t need, so they got deleted from my MacBook Pro and the ones I use and want got installed on my Mac mini so I can use them them on it.
BTW, I found the freeware app EasyFind (see App Store) to be very useful in tracking down a lot of these 32-bit apps that were not located in the Application folder. I got the file name from the About This Mac --> System Reports --> Applications report, then entered it in EasyFind and it found where they were. I then deleted the ones I wanted to get rid of.
Still not sure if I'll upgrade to Catalina, but it was good to go through and delete a lot of the old 32-bit stuff I don’t need or want. I’ve been needed to do that bit of housekeeping for a long time!
One of the Catalina features I was a little interested in won’t work with my MacBook Pro 2014. Although my iPad Pro qualifies to work as a secondary screen, Apple chose to exclude my MacBook Pro model from the list of qualifying Macs, so I’m pretty much SOL with that feature.
