Not yet upstreamed, waiting for positive feedback
that it actually works.

Index: capture_nrf_52840/capture_nrf_52840.c
--- capture_nrf_52840/capture_nrf_52840.c.orig
+++ capture_nrf_52840/capture_nrf_52840.c
@@ -17,7 +17,11 @@
 
 volatile int STOP=FALSE;
 
+#if defined(SYS_OPENBSD)
+#define MODEMDEVICE "/dev/cuaU0"
+#else
 #define MODEMDEVICE "/dev/ttyACM0"
+#endif
 #define CRTSCTS  020000000000 /*should be defined but isn't with the C99*/
 
 #define CHECK_BIT(var,pos) ((var) & (1<<(pos)))
@@ -317,7 +321,12 @@ int open_callback(kis_capture_handler_t *caph, uint32_
     bzero(&localnrf->newtio, sizeof(localnrf->newtio)); /* clear struct for new port settings */
 
     /* set the baud rate and flags */
+#if defined(SYS_OPENBSD)
+    localnrf->newtio.c_cflag = CRTSCTS | CS8 | CLOCAL | CREAD;
+    cfsetspeed(&localnrf->newtio, BAUDRATE);
+#else
     localnrf->newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
+#endif
 
     /* ignore parity errors */
     localnrf->newtio.c_iflag = IGNPAR;
