At work I migrated workstations and laptops from Ubuntu MATE 16.04 to Debian 10.
I spent about two months preparing, a few hours every other day or so. The preparation helped. I updated the imaging station with Debian 10 and from that successfully updated each workstation and laptop. The imaging process was nominally more complicated because of a need to retain user profiles. That went well as each user logged in and saw the exact same desktop as when using Ubuntu MATE. Future imaging will not have that need.
There were no disruptions or loss of business continuity. No user complaints.
One user offered that the systems seemed faster. Without the usual Ubuntu “kitchen sink” overhead the systems do boot and shut down faster. The systems likely do run faster without that overhead.
The owner logged into one workstation and never noticed.
I am pleased.