A good option to record screen on your Android is the AZ Screen Recorder. You can download it from here.
To make the recorded video more clear for a viewer, it is a good practice to show tapping and swiping on the video.
You can read an article on how to enable it on your Android here.
Steps to use AZ Screen Recorder are as follows:
Download the AZ Screen Recorder app and launch it
You can see options to recording, taking screenshots, live streaming, and more
Select “Record” option
Confirm the screen recording
You can stop the recording by swiping down to your notifications and tap on the “Stop” button.
When you are not recording, the app keeps its logo overlaid on your screen to quickly access it. You can remove it by dragging it down to the X at the bottom.
Things to keep in mind
Please do not use screen mirroring for your recordings as this gives an impression that real devices are not used while testing.
In Testlio, a video screen recording attachment has to be less than 10 MB and in .mp4 format and with a minimum resolution of 720p.
That means you will need to convert and reduce the size of your video files before you attach them to your issue report.
In case you will need help resizing and converting video files, use Tips from the Network article.