Have you tried asking, you know, on the TIC-80 page? There's an active community, and the creator lists many other ways to contact them as well.
Viewing post in Linux 64-bit tic80 -fullscreen not working
Ok will do but it seems someone else asked this question more than a year ago and was left unanswered ( https://itch.io/t/300533/tic80-fullscreen-not-working)
Thanks for the link