I haven't tried to compile the kernel myself but as far as I can see it's running a mainline 6.6 kernel, from 2024. I would not expect any issues when trying to update it to 7.3.

It might even be possible to replace the kernel in the image by the newest postmarketOS kernel to upgrade.

I haven’t dug in too far, but I found this website that sparsely has a 1-click installer ready to go.

https://openstick.org/