I have a tvheadend running on a Pi 4.
It looks like this (in TOP) when there are 2 TV channels active, I use a "Hauppauge WinTV-dualHD" as receiver.
For me it works fine.
Tasks: 185 total, 1 running, 184 sleeping, 0 stopped, 0 zombie
%Cpu(s): 1,1 us, 1,6 sy, 0,0 ni, 97,1 id, 0,0 wa, 0,0 hi, 0,2 si, 0,0 st
MiB Mem : 3794,3 total, 3045,9 free, 227,4 used, 520,9 buff/cache
MiB Swap: 100,0 total, 100,0 free, 0,0 used. 3457,3 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
645 hts 20 0 318976 35828 13544 S 8,9 0,9 4:59.35 tvheadend