steinmb

My MBP A1260 just died, nothing special lead up to this. It have been trustfully been working for 2.5 years. No startup...

Sound like you have tried a lot of stuff. I know you have an iphone 5 though you might still have the same issue. iPhone 4S (and older) with a dirty/defect docking connector showed just these symptoms. You should check your lightning connector. Start by cleaning it prperly. If that does not help, try to replace it.

I would start with replacing the broken power button. You will find it on this site. I do not think it cost more then about 20 USD.

Yes it is. Have a look at the iPhone Display Adhesive Replacement guide

The video show battery removal without taking out the taptic engine first. So, what is the recommend method?

I had to use a TR5 on the RAM cage. TR6 did not fit.

2018 and 2020 are identical machines. Apple only upgraded the default file storage. There is no such thing as a 2020 Mac Mini really.

This is the most delicate part of replacing the RAM. Be very care full when open the lid and removing the WiFi connector.