I've tried following video instructions. But each time, after 10 mins I felt like I was making zero progress. Perhaps I just need to keep trying and eventually it will click?
Or perhaps I should ask one of the neighbourhood kids?
If you insist on skateboarding, larger diameter wheels go a long way to not crashing on every crack/pebble/uneven surface. A long-board is easier than a street/short-board, and will usually have larger wheels by default.
Beyond that I have no advice for learning in your 40s. I learned to skate street in my childhood and can still effectively get around on one in my 40s. But it's no joke to crash on pavement at our age. Be prepared for some slow-healing fractures and irreparably damaged laptop/phone if you're commuting with a tech job.
Having said all that though, skateboarding is awesome and should get way more respect than it tends to. Super challenging and rewarding, more kids should learn it, character building.
Depending on where you live, sidewalk construction may be an issue. E.g., paved areas in the UK can be shitty due to inconsistent height between paving stones. The slightest thing and the newb is gonna go flying.
The thing to remember with skateboarding is that for every several minute video showing cool tricks, you aren't seeing the hours of bails. The Tony Hawk games always included bails videos to show that there's a lot of perseverance and pain that goes into making it look effortless.
I did myself some horrible injuries over the years, including slashing the palm of my hand wide open on a pebble-dashed wall whilst learning just to coast. Also gave myself a horrendous groin injury at one point whilst casually riding around.
It's still good to cover short distances, and you can learn it in an hour and not fly off on every little pebble.
Ideally get one with bigger wheels.
On a relatively firm surface (ie: carpet) this provides some practice for the balancing act. How foot placement and the contours in the board impact things too
Similarly, on something with a little more flex (grass), it's a decent way to start trying some flip tricks :)
As for rolling around, I think it's mostly finding really smooth/flat surfaces... and just doing it a lot.
Depending on your wheels/weight placement, anything thicker than a quarter can stop you almost immediately.
It takes a little while to get the 'feel' and speed to deal with rougher surfaces particularly well
The 'kicking off' motion is pretty tricky, compared to say - standing normally, rolling down a driveway.
Instead of just managing balance side/side, front/back gets really important with only one foot on the board -- it wants nothing more than to shoot forwards/backwards, depending on where you're leaning.
Some familiarity with standing on it is key, mainly because kicking requires a lot of balance/control -- one leg/knee is doing a lot of work. It's holding you above the board, but it's also holding the board under you
Standing with one foot on it and rolling back/forth and getting a feel for it can help too. Finding how sensitive the shifts can be and how much 'locking' is necessary to make the transition from kicking to standing
Try to avoid learning to push in the 'mango' style; planted foot on the back of the board.
Like a Dodge Viper, there's a lot of nose - it's hard to steer/keep under control.
Planting your foot near the front of the board is better for keeping control and powering through rough terrain. Near the back, it'll wander/bounce like crazy
There's no one good spot, but roughly on/just behind the front trucks is a good place to plant for pushing
You could try a hub driven electric board, supposedly they can be freewheeled without the motor like a heavy passive skateboard to increase your practice time, which musicians and gamers call shed time or seat time