Sorry about the appearing/disappearing message. I realized that I had uploaded a version of the conf file without the FTP passwords obscured.
After a great deal of hair-pulling, I have got all the services that I have on my 'workhorse' Pi 3 under Bookworm, including weewx (I thought!) working under Trixie. I then found that weewx was running, storing my weather data correctly in my remote MySQL database, and generating the two different sets of reports I respectively use for home consumption and 'publication', but it wasn't FTPing the generated files intended for publication to their target systems (or anywhere else). No relevant errors were being reported (with debug set to 0 in weewx.conf); the FTP transfers were just not happening. Setting debug to 1 in weewx.conf did shed some light on the problem. As you can see in the attached log file, the ftpgenerator reports: "FTP upload not requested. Skipped." The identical reporting section (extract also attached) is working fine in my Bookworm installation. Can anyone shed any further light on this?