Only apps/router example uses dlmstp_linux.h\c within the library. The other example apps use dlmstp.c for MS/TP datalink.

The MS/TP baud rate for the example applications typically use environment variables - see dlenv.c module:

 * - BACDL_MSTP: (BACnet MS/TP)
 *   - BACNET_MAX_INFO_FRAMES
 *   - BACNET_MAX_MASTER
 *   - BACNET_MSTP_BAUD
 *   - BACNET_MSTP_MAC

Is there something that should be changed to better support your implementation?

There are a couple of ways to use BACnet MSTP in the library:
a) with a microcontroller, single datalink, BACDL_MSTP defined.
b) with the example apps running on Windows/BSD/Linux, single datalink, BACDL_MSTP defined. Note: the MS/TP datalink app must join the MS/TP network segment, which may take up to a minute , prior to accomplishing its task. Therefore, the apps/server (or gateway) are really the only appropriate apps to use in this manner.
c) BACnet/IP to MS/TP single purpose router, dual datalink - see apps/router-mstp for details.
d) general purpose BACnet router on Linux, arbitrary number of datalinks - see apps/router for details.

Note: the apps built for BACnet/IP can route through either BACnet/IP to MS/TP router...