Any issues updating from Catalina to Big Sur?

I just updated from Mojave to Big Sur on macMini 2018.

I tested all my critical apps a few weeks on an external Big Sur disk (did the same in Catalina but skipped it).

I tested BBEdit, KeePassXC, Carbon Copy Cloner, GraphicConverter, exiftool, Xcode command line tools, MacPorts, Photos, Final Cut Pro, LibreOffice, Dropbox, Canon scanner, Cisco Anyconnect, VMware Fusion, WhatsApp, Spotify, Firefox, VLC, Handbrake, IINA etc...

Then I decided it was time to move on although I will miss some old 32-bit apps (Photoshop CS6, Lightroom 6.14, MPEG Streamclip, QuickTime Player 7 Pro).

Then cloned the old internal disk to an external SSD and HDD with Carbon Copy Cloner.

Then downloaded Big Sur installer and made a bootable USB flash drive from it, booted it to its Disk Utility, took a deep breath..., and reformatted the internal SSD device (not just the volume) as APFS (GUID), and cleanly installed Big Sur to it, and installed apps that I need to it (I occasionally do this kind of spring cleaning to save space in major system updates).

Then restored my and other users' data files from the CCC backup manually (old iTunes folder and Mail needed special attention -- ask for details). Migration Assistant would have been an option but I prefer manual transmission.

I kept the old Mojave clones a few weeks and then started to use them as Big Sur CCC backups when I was certain I didn't miss anything. I made a small 30 GB APFS Mojave volume on those CCC backup disks with those old 32-bit apps installed although I also have Snow Leopard Server, El Capitan and Mojave as VMware VMs in Big Sur with those 32-bit apps for light occasional use.

Big Sur has been OK. It boots somewhat faster than Mojave and has been stable. Photos.app has some bugs that I was aware of and have workarounds (I have my main photos archive in plain folders elsewhere and use Photos only as a viewer and an aid to sync to iOS devices).

RoaringApps is a crowd-sourced App compatibility lookup service. May find info on Big Sur compatibility with your apps, there.

Quicken has always been problematic with macOS Upgrades, but I don't use it or know specifically about Big Sur.

Check that your printer/scanner is supported in Big Sur. It seems a lot of manufacturers haven't provided drivers for Big Sur.

If you are using it wirelessly with your MacBook Pro, then it is most likely using AirPrint, so should work in Big Sur.

There has also been sporadic issues with external monitors not working. I don't know that I have seen any pattern, though.

The UI has changed a bit. Some people hate the look.

Yes. For example, some folks have had trouble upgrading from ancient iPhoto libraries to current Photos (Apple had a converter for some old upgrade point). Or wondering why old obsolete video codecs don't play anymore although QuickTime Player did offer to convert them in Mojave.

I had some trouble even upgrading Mail from OS X 10.10 to 10.11 -- in older OS X just copying ~/Library/Mail was OK but then, after going through many hoops, I had to use Emailchemy to properly convert old mail. After that Mail has imported old Mail folder OK.

Matti Haveri wrote:

I just updated from Mojave to Big Sur on macMini 2018.

Big Sur has been OK.

It is always advised to stay current in both the hardware and software.