Hello,
I suspect this topic is becoming obsolete as people acquire new hardware that includes onboard 5G wifi capability, but in case others continue with the OSMC adapter, I thought I’d post my experiences in case they might be helpful.
My SD card quit on me last week, so I had to acquire another card, re-install OSMC, and reconfigure everything from scratch. By far, the biggest problem I had was configuring the OSMC 5G wifi adapter. I had so much fun with it I decided to do it twice! 
(The first “new” SD card I installed was defective so I had to install on another one!) Here is a summary of my most recent experience, which took at least two hours:
I installed OSMC to a blank SD card and specified a wired connection initially because I knew the wireless connection wasn’t going to work. Once I verified that OSMC was installed successfully on my RPi 3B, I added the line dtoverlay=sdhost to the config.txt file using My OSMC>Pi Config. Then I disabled the wired connection and enabled the wireless connection, unplugged the ethernet cable, plugged in the OSMC adapter, and rebooted. (The wired connection could only be temporary for me, as I had to lay wires across my floor to do it.)
Once OSMC was back up and running, I went to My OSMC>Network and ensured that wireless networking was enabled and wired was disabled. The OSMC adapter was “seeing” many networks, some 2.4G, others 5G, including my 5G network. I attempted to connect to my 5G network, and the result was the dreaded “No internet”. I know now from Sam that I should have posted output from route here and and asked for help in diagnosing this further. Not realizing that, I rebooted and tried to connect again. No joy. “No internet”.
Next, I moved on to using the move command to move the template .dat file to the .dat file:
sudo mv /lib/firmware/mt7610u_sta.template.dat /lib/firmware/mt7610u_sta.dat
Before I did that, though, I examined the contents of the /lib/firmware directory and noted there was no mt7610u_sta.dat file there. I expected there to be one as a result of the configuration process. Was my expectation wrong? Pressing on, I moved the template file over and rebooted.
The result was I was able to get a 5G connection. Also, the adapter only sees 5G SSIDs now. I ran iperf3 and observed that the performance was between 30 and 40 Mbits per second from the server – not up to par for a 5G connection. So, I edited etc/connman.conf and added the line BackgroundScanning=false. Upon rebooting, I ran iperf3 again and observed performance around 80 Mbits per second. That seemed to be within the acceptable range, but rather than accept that and move on, I decided to tinker more.
I looked at the mt7610u_sta.dat file and noticed the following lines
CountryCode=
WirelessMode=8
I decided to edit this file and change these entries (only) to
CountryCode=US
WirelessMode=13
I’m in the US and my router has both 2.4G and 5G radios. The reported wifi mode for my router’s 2.4G radio is 802.11n/b/g, and the wifi mode for its 5.0GHz radio is 802.11n/ac. For the OSMC adapter, wireless mode 13 apparently maps to g/n/ac in 2.4GHz and 5GHz, so WirelessMode=13 seemed like a good choice.
I made these changes and rebooted. The result was “No internet”. I waited a bit and rebooted a couple times, but still no joy. So, I guess my greediness was not going to pay off, at least not with those entries in the .dat file.
I put the above entries back to their original values and rebooted. No internet again. I reasoned that I needed to take the background scanning entry out of connman.conf and reboot. I did that and got a connection at 5G. iperf reported average speed around 25 Mbits per second with some intervals reporting 0. So, the connection was slow and erratic. Then I went back and put BackgroundScanning=false into the connman.conf file and rebooted again. iperf now reports speeds to the RPi of around 60 Mbits per second and speeds from the RPi to my server of about 75 Mbits per second. At that point, I decided that was good enough and quit.
I suspect I’ve ended up in a spot that’s adequate for my use, but if anyone spots anything “interesting”, I’m always willing to tinker. If for some reason I conclude that I’m not in a good spot, my next step is to get a RPi 3B+, which has onboard 5G wifi that supposedly works well. In a year or two, the choice between the RPi 4 and the Vero becomes much more interesting to me.
Thanks again very much for the great support.