If you're not in a hurry, then I'd take a step back and not get lost in the weeds.
I wouldn't rule out any category of bike just yet. Many people, myself included, can happily ride for several hours on "race" bikes. Or maybe your preferences drift and you get gravel-curious. You've just started your journey - be open to letting it wander while you find your legs.
At this point, I'd think about the practical: considering gearing changes for your current bike. This may be as easy as a new cassette or it may be as simple (but not easy!) as getting stronger. Take a look at the tooth count for both your chainrings and your cassette cogs, consider the terrain that you ride and go from there.