I used to travel a lot for work, but not as a pro pilot. My work schedules were odd too, working in a shiftwork industrial setting. As an engineer most was regular-ish daytime hours but lots of overtime, nights, and weekends.
To make matters worse, these were in the days before internet.
and to make matters even worse than that, I was mostly traveling to small paper-mill towns with not much to do, not many choices for dining out.
A lot of very long days so I pretty much crashed when I got to the room, but I spent a lot of dead downtime too. When I think back on what I did, mostly what comes to mind was doing work. Just out of boredom in that time back in the room after dinner but before bed, I'd pull out the computer and work on my data spreadsheets, sketch design ideas, catch up on emails (with dial-up modem), etc...
I think that with internet what it is today, I'd likely find myself in the youtube rabbit hole a lot...but I think that I'd also find myself researching the topic-of-interest for the month. Seems like I've always got something I'm fixating on...wether it be trying to find a replacement prop for my old outboard boat engine, or what's the best way to repair xyz, or the latest thing that came to mind the other day and I jhaven't made the time to research it yet...how to keep my toll road transponder's suction cups form failing and dropping the thing onto my dash. I'd like to thik taht with internet what it is now, I'd take on something more meaningful, such as learning another language, but I know that I likely wouldn't.
I like
@Randomskylane 's suggestion of writting a book. My favorite genre is autobiographies/memoirs, mostly military. I've often considered that writting a book to get my stories recorded would be a nice way to leave a little mark on the world... but I just don't feel that I've got very many stories that anyone would be interested in reading....partially because my memory is just too fuzzy but mostly because I haven't done anything adventuresome such as dogfight against the Nazis or make my way through viet-cong held jungles. All the travelling I did for example. All the towns have sort of run together. I've forgotten people's names, etc. I threw away my old paper daytimer calendar years ago taht would have been helpful to piece together a little bit of that and I have no other diaries or documentation to help.