The wikipedia page for Free time (music) lists Charles Ives' Concord Sonata, and most of Kaikhosru Shapurji Sorabji's music alongside Erik Satie as examples. There are a few more contemporary examples in the article, it is worth a full read.
Free jazz and Free Improvisation are also related and mentioned in the article, although don't really give many examples that would resemble Satie's music.
This reddit post asking the same question is helpful, mentioning Debussy, Frederic Mompou, Ravel, Poulenc, and many others. Personally I think that Ravel's work most closely relates to Satie's.
Free time is generally much harder to perform, describe, and relate to a listener so it does make sense that its use is much more limited compared to other more common rhythmic devices.