All four are the same error code and all four cite the same lrtsal.sys driver as the cause and as you note there is absolutely nothing on the internet concwerning this driver.
Here is my suspicion: Companies like Dell, HP, Toshiba, etc. will load their own drivers rather than third party drivers and this can often lead to issues such as you are dealing with. This may be your issue here.
I would contact Dell tech support, tell them that every BSOD error is the same error code 0xD1 and tell them that it is always this driver.
However, before doing so, in light of when these BSODs occur go to Dell's websight, find your exact model, and download their latest internet/wireless/NIC drivers, onboard sound drivers and onboard video drivers for your system. Does this bring stability?