I use TVMosaic addon to connect to Synology recorded TV (DVB-T).
With interlaced content in standard definition MPG2 video is stuttering going fast and slow alternate.
It is hardware decoded MMAL.
If I set deinterlace on off or on half, it is ok (maybe not perfectly smooth, but mainly ok).
LIBREELEC 9.2.0 ON RASPBERRY PI 4.