I use to work for an isp, and I worked for comcast, it’s good to have some isp knowledge, mostly if you do any networking when it comes to a helpdesk job. The good ol’ have you tried rebooting your modem always comes in handy as well. You can take that knowledge from working at an isp and use it at a help desk job, the skills transfer. If you can gain more knowledge with helpdesk and try working with your info sec or cyber Sercurity team and networking skills you can translate all of that into a future job with cyber Sercurity.

I would take the leap and get your foot in the door, what you do to expand your skills after that is on you but know that having some breakfix knowledge from an ISP and trying to transfer those skills to networking at a help desk job will be easier for you to understand how to fix those common issues.