If you download the full Sage 300 2021 ISO image, run the main set up, CRM will be included but the included version is CRM 2020 R2. If you want to install CRM 2021 R1 you must download Sage CRM 2020 R1 from here:

CRM 2021 R1 Full install for standalone CRM and for Sage 300

Then you need to download the R1 patch from here.

There is also an update here which needs to be installed the above.

The integration module should be included in one of those. I hate how you have to go around the houses to get all the bits instead of a page that shows the support matrix and links direct off the matrix instead of KB numbers written in text that you then have to search for.