If your kid is having troubles leaning to ride a bike, I would suggest trying one of the bikes from Woom (https://woom.com/). Especially in the smallest models for 4-5 year olds, these bikes much lighter - almost half weight - than a lot of the alternatives. They also cost a lot more, but the high resell value makes up for some of this.
This is one of the biggest hurdles to getting kids to enjoy riding bikes too. If you think about the weight of many cheaper kids department store bikes they are a significant weight compared to the child. Having a lighter bike makes it much more enjoyable for the kids.
Also recommend Islabikes and Frog bikes for two companies that offer lighter offerings. Again you have to pay for it, but they can often be resold and a decent value later. Especially if you keep the bike clean and loved.
I have a mechanical engineer friend who's deeply interested in bikes, he recently designed and welded his own DIY cargo bike, he gave me an hour long lecture on the evolution of frame geometry and alloys when I asked him to help me pick a second hand bike, etc—and he's very, very impressed by Woom bikes. I got one for my kid and the engineer will just look at it, admire the parts and go "oohh yeah now that's a bike."
They also have balance bikes.