Are there points of no return or lockout for side content in Red Dead Redemption 2?
Solution 1:
There is at least one achievement/trophy you can miss if you simply power through the story: you need to fulfill 5 camp companion requests and will not be able to do this if you progress all the way to the epilogue. You can also miss opportunities asking since some companion requests are restricted to specific camps.
There are some other side missions that are chapter specific, as time does pass at the rate of weeks, months, and even years through the story.