OpenRCT2 is the free and open source game engine reimplementation of RollerCoaster Tycoon 2, adding in many advanced featured and cross-platform support.
Another new update is out now with the v0.3.1 "Self Defence Against Fresh Fruit" release that went up on September 27, 2020. Quite a wonderful sounding set of new features too like 2x and 4x zoom level options (which require the use of the OpenGL renderer), there's a new API for listening and communicating over TCP which they mentioned could be used towards things like Twitch integration, their API expanded to expose more for people to hook into like scenery placement / removal and there's even new snowy weather types like a blizzard.
More bugs were also squashed with this release, some of them sounding pretty funny. One particular bug had entertainers making themselves happy, instead of guests. Imagine that, a person with a bunch of balloons round the back of a building just making shapes for themselves and telling everyone to go away - how rude.
The team behind OpenRCT2 are a dedicated bunch and it's quickly become the ultimate way to play RollerCoaster Tycoon. You can find OpenRCT2 here, plus grab the required data files from RollerCoaster Tycoon 2 on GOG.