Windows 10 has inbuilt screen recording software in the Windows GameBar. Unfortunately this recording is geared only towards games and is App specific. You will only be able to record within one open App and are not able to record across Apps or the Desktop:
The best free screen recording software I found for Windows 10 and Ubuntu 20.04 is VokoScreenNG.
I used to really like Debut Video Capture but feel it has went particularly downhill in later versions in terms of both user interface and has introduced annoyances such as timer countdowns when beginning a recording. It also seems to be less reliable on newer Windows 10 builds.