Kansas City has some fantastic trail systems
https://urbantrailco.com/the-trails
WyCo, Smithville, Swope and Shawnee Mission are probably the top 4 mtb trails. There are also paved trails within a short distance from just about anywhere on either the KS or Mo side

KC has a good bike community. I am in Olathe (Home of Garmin HQ) so a lot of people around here are used to cyclist on the road as the Garmin crew has daily lunch rides. No that doesn't mean they ALL give you the space but people are pretty good with it. We, like many cities used to have a lot more tris in the area but that has dropped off greatly the last 5 years. Good ones to hit up are - KC Tri, Shawnee Mission Park Tri (if it doesn't storm that year), and Matt Mason Cowboy Up Tri. Also Johnson County Parks and Rec host a Kids tri and used to be womens only tri but just this year opened it to all genders. TriKC and Midwest Tri Coaching are groups to look up and Elite Cycling in Leawood, KS is the home for all things Tri in South KC. And as stated some of the best MTBs and builders around. Localcycling.com/kansascity has a lot of info on local road/mtb/cx racing also so check them out. Hope that helps!