Or is this a limitation of the SX280 port?
It is, GPS support has not been implemented. I'll see if I can change that.
Thank you for trying!
Another thing I noticed is that Canon stopped updating the data file with satellite positions, downloaded to the SD card via the camera's menu, that is needed for the A-GPS (assisted GPS) feature of the SX280 HS to work. Accd. to
https://hobbyelektronik.org/b/tag/a-gps/, they announced that mid-2019 and stopped updating the file at the end of 2019. It's still there at
http://gdlp01.c-wss.com/rmds/ic/agps/cagm01.eed (which is a Canon server), but hasn't been updated since.
The same blog as mentioned above says that Mediatek, the manufacturer of the SX280's GPS chip, still provides the regularly updated file at
http://epodownload.mediatek.com/EPO.DAT, and Sony (apparently using the exact same GPS chip in some models) provides the same file (different name though) at
http://control.d-imaging.sony.co.jp/GPS/assistme.dat. I've downloaded both and compared them, and they are identical to each other while sharing the same format with the file on the Canon server, but having a different (presumably up-to-date) content.
So I have taken the EPO.dat file and saved it as cagm01.eed in the GPS folder on the SD card, replacing the original file. I imagine it works because the SX280 for the most part gets a satellite fix rather quickly, though I would need to test how long it actually takes with A-GPS turned off compared to A-GPS turned on.
In the event that this alternative file does indeed work for the SX280's A-GPS, would it be at all possible to have the camera download the file from the alternate Mediatek URL mentioned above? Or is this a totally crazy idea, not possible, not worth the effort, ... ? I suppose it's not worth too much effort, updating this once a month or so manually is quite manageable.