I was trying to download DRM protected streamed video, it not worked, so i have tried two Linux software for the screen recording. Here is my review:

1. VokoscreenNG
Recorded volume may be controlled by clicking the speaker icon in the bottom system menu and clicking mixer. Then during recording volume control should be visible.
CONS: no keyboard shortcut to start/stop recording, no VP9 & HEVC support at the time of writing

i ended up discovering that the best, most compatible format with even a bit older TVs should be MKV, VP8 video codec and Vorbis audio codec.

2. SimpleScreenRecorder
can save multiple presets, can use keyb. shortcut, more detailed functions, can optimize to a bitrate of choice, shows to support 5 CPU
CONS: no VP9 & HEVC support at the time of writing

i ended up recording at 25 framerate, scale video ticked (is easier on CPU), MKV, VP8, 700kbps, Allow frame skipping, Vorbis audio codec 128kbps

3. FFMPEG - not so convenient, but can use latest codecs and hardware acceleration if you take time to compose right command:
ffmpeg -fflags +igndts -video_size 776x549 -framerate 25 -f x11grab -thread_queue_size 512 -i :0.0+299,232 -f pulse -ac 2 -thread_queue_size 4092 -i 0 output.mkv
ffmpeg -fflags +igndts -vaapi_device /dev/dri/renderD128 -video_size 776x549 -f x11grab -thread_queue_size 2048 -i :0.0+299,232 -f pulse -ac 2 -thread_queue_size 2048 -i default -vf 'format=nv12,hwupload' -c:v hevc_vaapi -qp 28 -framerate 25 output4.mkv

legend: 299,232 - coordinates where the video frame (776x549) starts. 299 pixels from left and 232 pixels from top
vaapi_device - found when doing "ls /dev/dri" more details: https://trac.ffmpeg.org/wiki/Hardware/VAAPI
hevc_vaapi - encoder list of supported: "ffmpeg -encoders 2>/dev/null |fgrep vaapi"

Do you know other good software for the task?