Current KANBOARD Application version: 1.2.22 has no full .svg support. You can attach such files, but in the attachment handling dropdown the “view file” option is missing.
An Instruction how to add support you find at github Add support for .svg pictures #5034 (thanks a lot to user sulisu).
It would be great if some users could test that
Be careful and save the original files before you do the changes in kanboard/app/Helper/FileHelper.php and kanboard/app/Helper/FileHelper.php! You never know …
Please tell your test results here or on github #5034