The Source port of the original Deathmatch is famous for its "glitchy" charm. Some players prefer older, non-updated versions because the "SteamPipe" update in 2013 introduced several bugs: Half-Life Wiki Broken Maps : On the classic map
Searching for "Half-Life Deathmatch Source download free non-steam" often leads to sites like SourceForge or various "repack" forums. Be cautious with these because: Guide :: Play in Half Life 1 for free - Steam Community half life deathmatch source download free non steam