The most direct way to get a deathmatch experience is by installing the CSDM plugin. Here is a general guide based on the classic method for Counter-Strike 1.6, which is highly similar to the process for CS 1.1 servers.
: A massive archive specifically dedicated to older Half-Life and Counter-Strike versions. AlliedModders
While any map can be played as a Deathmatch, these were favorites for the fast-paced 1.1 era: cs_mansion : A classic, small-scale map from the beta/1.1 era. de_dust / de_dust2 : The legendary maps created by Dave Johnston that remain the gold standard for layout balance. fy_ice_world