Anecdotes from an independent repair shop owner / operator.
I very rarely encounter reparability issues from Lenovo devices. I’ve worked on the full range down to Chromebooks and all the way up to high-end ThinkPad workstations. Parts are generally available, if not from Lenovo then on the aftermarket. They have repair documentation on their site. There are cases where the memory is soldered, but that is not something that is unique to Lenovo.
From my perspective, the least repairable devices end up being the LG and Samsung laptops. Parts are much harder to come by, which means that when they are available they’re usually quite expensive. Their designs are hostile to repair, documentation has not been readily available, they haven’t used modular memory for about 10 years now.
Microsoft’s Surface lineup has historically been real bad for repair, it’s not until recently that they’ve been turning a new leaf. Their logic board designs are so unusual that even component level repair becomes a huge pain compared to others.