Please note that the JBR is a custom build that contains a number of important changes and fixes, and it's not recommended to replace this. For M1 support, it's much better to use an M1 compatible JVM and .NET runtime. Rider 2021.2 is an Intel build, because when it was released there was no M1 compatible .NET Runtime.
Rider 2021.3 has an M1 build, and makes a big difference. It's currently in preview (https://www.jetbrains.com/rider/nextversion/) but will be released in the next week or so.