Forerunner 255 Music Navigation

The watch does not support maps, but it supports routes. You can make them yourself, or download routes from others.

Would you have any tutorial teaching how to create these routes or any topic to instruct? Thanks in advance.

There are several ways to make routes. Garmin has an editor here:
https://connect.garmin.com/modern/course/create

I prefer to use Strava, but it requires paid membership, I think:
https://www.strava.com/routes/new

I go into the Garmin Connect Mobile app and follow the menu > Traning and Planning > Courses > Create Course. From there I was able to get into a map and choose my own hiking path on a map, then send it to my device.  Ovekvam gave a link to similar functionality on the website.

Once it is added to the device, you can then "follow a course" on the watch.  The way I know how is to use an extra menu while starting an activity.  E.g. for a hike I would

1. press START
2. scroll to my activity type Hike and press START again, so it starts looking for GPS but hasn't started timers yet
3. press UP to access menu, instead of where you normally press START to activate the timers
4. scroll to Navigation and press START
5. scroll to Courses and press START
6. scroll to the desired course and press START, so it shows "loading" and then a course overview

I forget how many more START presses it takes but eventually I get to where the activity timer starts and the normal screens are available to actually start hiking.

It's a shame a watch as good as this one lacks map features and only has the option to create routes. Is it possible through updates to add this function, if Garmin wants it? Do you have hardware for that?

The 955 is almost the same watch, but with map support, at a higher cost.
But I suggest trying routes. It works rather well without maps.