Sounds like a problem (bug) in the GUI then, that it does not allow you to make them blank.
As a workaround, you can try editing the file where that configuration is stored, look in the directory /etc/NetworkManager/system-connections/ where there should be one file for each connection, the filename should be like the connection name. Inside that file, you can probably remove the lines mentioning username and password, then reboot to make the changes take effect. Maybe save a copy of the file somewhere before editing it.
Is this in settings under mobile and access point names? Is it possible to add a new APN with the “+” sign without username and password, and forget about the old one containing a password?
Thanks. That got rid of it. I retyped the APN name, and can now send text as before. Searching here, I see a lot of similar issues trying to send/receive text with image. Doesn’t seem to be a fix yet.
The"Send SMS" works
The Send SMS/MSS opens create a group.
Ah. I just realized that the editor for this thing decided that bracket @ bracket has to mean the copyright (@) symbol.
The confusion was/is MMSC .
For me, it’s the reverse “SMS and MMS” > and under MMS Carrier Settings it asks for MMSC
It’s all sorted out now. I think. At least it now sends/receives text w/ pics.