GrapheneOS on Koodo Pixel 10 ?

Nothing on the Koodo side stops you. The Tab is just financing spread over 24 months, the phone is yours, and Koodo has nothing to do with the bootloader.

Two things though. New phones might  with a 60 day security lock to the Koodo network. That is a SIM lock, separate from the bootloader, and it comes off on its own after 60 days or sooner if you ask through Koodo Assist https://www.koodomobile.com/en/help/unlocking-your-phone

As well, I would test VoLTE and Wi-Fi calling right after you flash. Koodo certifies specific models for VoLTE and I wonder if a custom ROM stays certified. If it doesn't work out you have 30 days to return an online order.

Thanks for the quick reply. I pulled the trigger and will report back when I get the phone.