Are all of the third party ones you use compatible with Big Sur?
Well, first the failures.
Microsoft OneDrive - I just couldn't get it to behave. It kept saying it was up to date then it would resume syncing. When I tried to work with it, response was very sluggish. I managed to go into the preferences to deselect some folder that I didn't want sync'd; OneDrive just reported some error when I clicked OK.
Discord - Initially it worked. After waking from sleep I only got a blank screen. That persisted even after restarting Discord.
Everything else I tried worked. All programs were at their latest versions as of today, except for Arq (I'm still on version 5) and MoneyDance (I have version 2017 installed). I just ran basic tests, at most 30 seconds each program. Without further ado, here are the winners: (all worked flawlessly)
DevonThink, DevonAgent, OmniFocus, OmniGraffle, OmniOutlier, Arq, 1Password, BBEdit, Dropbox, Firefox, ForkLift, Excel, OneNote, Outlook, PowerPoint, Word, MS Remote Desktop, Microsoft Teams, MoneyDance, PCalc, Scrivener, Skype, SmartGit, Viscosity, WiFi Explorer, WireShark, Murus Firewall, Luna (using a Mac as a second display), LaunchBar, iTerm, iStatMenus.
I don't have the development environments I use installed on this machine. I'll have to do that and test thoroughly before I upgrade my main machine. Other programs that are just on my main machine would not cause me too much grief if they didn't work.
As I write up this post on my 15" laptop screen, I'm dazzled by the aesthetics. Then my world shatters. I try to drag Safari around to move it out of the way of my notes and I repeatedly fail to grab a spot that works; I almost clicked the back arrow when I was halfway through my writeup (yikes). Safari could never be my main browser because of this. It would be tolerable to use with a real mouse, but with just the trackpad it's terrible.