When a new version of PixInsight is released you will recieve an email anouncing it with a link to the Software Distribution System where you have to download the new version.
For Linux installation, uncompress it and run the installer program as root:
Using "su" command: su -c './installer'
Using "sudo" command: sudo ./installer
The installer program will remove the previous version and install the new one.
See more information here.
Note: New versions cannot be installed through the update system
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