I also bought for that, but need an adapter. Something like this https://www.ebay.com/itm/223146302041. I have another one, I can send it to you.

The M.2 2230 SSD type is usually single-sided, which means that it only has components on one side. This enables a thinner design, which is useful in many modern laptops. To use this SSD in your ThinkPad L15 Gen 3, you need to make sure that the device supports M.2 2230 slots. However, the ThinkPad L15 Gen 3 only has one M.2 2242 slot, which means that the M.2 2230 SSD will not physically fit. However, you could use an adapter if available or consider another SSD type that is compatible.

I can't answer this conclusively as I don't know the structure of the Legion. But what I can say is that it can fit, I use this SSD in my Thinkpad Z13. The original is a 2240, but the WD is only a 2230, which is 12mm shorter than the original. In the Z13, the SSD is mounted under a copper plate as a heat conductor, I simply mounted the WD and it remains mechanically stable.

Technically the 2230 fits, but the heat development is a problem, the WD heats up quite well, the 11 Pro can't handle that well, I would recommend one of these two Silicon Power Dysk SSD Silicon Power UD90 1TB M.2 2230 PCIe NVMe (1000 GB, M.2 2230) Patriot SSD Patriot 1TB M.2 Viper Mini VP4000 Gen4 x4 5000/3500 (1000 GB, M.2 2230)

Torx T3 screwdriver According to a tutorial found on the net

Yes, it should fit without any problems.

This is correct, the SN770M is not compatible with the Lenovo Legion Go as it is an M.2 2230. The Lenovo Legion Go requires an M.2 2242 SSD: https://legiongolife.com/how-to-upgrade-your-legion-go-ssd/ According to this article, you also need an adapter to clone the SSD of the Legion Go. On Galaxus/Digitec I cannot currently find a larger SSD for the Legion Go than the one installed, at least none that is available. However, you may be able to find one from another supplier :)