Comment by RUnconcerned

I'm not sure RCT ever had a modding community, but it's predecessor, Transport Tycoon Deluxe, did. TTDPatch[0] had several gameplay and quality of life improvements, but it was eventually superseded by OpenTTD[1].

[0] https://www.ttdpatch.net/

[1] https://www.openttd.org/