The post you have on the BRARA website provides very useful instructions. I can verify that these instructions do work for Anytone radios. So I followed your existing instructions which include brandmeister website configuration settings to motorola, etc, and then performed the radio config commands.
But then I had to do some trial and error to get radio to cell phone text messages to work correctly. Below is what worked for me.
In the section of the article above which explains where to send the SMSGTE messages to, I sent the SMSGTE messages to 310999. This worked for me on both the BRARA brandmeister machine, other brandmeister repeaters, as well as my hotspot. No additional contacts were added to my existing radio codeplug.
Specific button presses for the Anytone 578 radio (I believe these are the same for all Anytone DMR radios):
Menu > Messages > New Msg
Type in the following: SMSGTE @<destination cell phone number> <message text>
-no spaces or hyphen in the 10 digit phone number. The message text can have spaces and punctuation
-example: SMSGTE @5551112222 House is ok. Everyone is safe.
Send > Manual Dial > Type in the following: 310999 > Confirm
As an optional step, I followed these instructions on the SMSGTE website to setup an account and aliases for SMSGTE. This helps you to configure aliases on the SMSGTE server. This would apply for both analog aprs smsgte messages, as well as dmr aprs smsgte messages.
Remember that the SMSGTE tool uses the APRS network, which is visible to the public. So setting up aliases keeps phone numbers out of view from the public. I setup an alias called “DAD”. So when I want to send a text message to my fathers cell phone, I can type: SMSGTE @DAD <message text>. Then the SMSGTE server knows the phone number to send the message to. It is also easier than typing out his ten digit phone number each time I want to send a message.
Lastly, you can use the aprs.fi website as a tool to view what is going over the aprs network, as a diagnostic tool whil you are setting this up. https://aprs.fi/ .
If you enter your callsign and then click the ‘raw packets’ link on the right, you can see all of your aprs traffic, including inbound and outbound smsgte messages.