i feed em into tvheadend.. which is probably a little more complex than most people care to mess with, but if you use libreelec/coreelec, it comes (mostly) preconfigured in the repo.. just hit install, go to the web interface on a browser, and add the m3us there. If you're not doing elaborate stuff like timeshifting and such, it's pretty straight forward.
there are many better options then using iptv and kodi
I combine mine with xteve and filter out unwanted channels
Tvmosaic plus their Kodi PVR addon enable you to combine multiple m3u and xmltv/epg sources. It also enables you to record (scheduled and directly) and use timeshifting
IPTV MERGE by Matt Huisman
Forget about Kodi for IPTV , it is just not good enough use this one /r/TiviMate