I actually have an update on this, and I’m fairly convinced the wifi chip (BCM4356XKUBG) is at fault.
I realized that I couldn’t detect any wifi networks or that straight up no wifi-capable device was recognized in Ubuntu/Lakka/LineageOS. Other users confirmed that the wifi chip could be responsible for preventing the Switch from booting. I think that maybe the solder connections are actually the problem, and not necessarily the chip itself, as many users have reported the problem to be intermittent. So a reflow, reball, or worst-case a replacement, of the chip should fix the issue.
I haven’t actually attempted a fix myself, as after leaving it on the shelf for 2 months or so it now magically started working again! And indeed Linux is now able to detect wifi networks. I’m guessing the SwitchOS attempts to communicate with the chip during bootup, and if that fails gets stuck somehow, while Linux doesn’t do this.
PS: For anyone interested, i actually found a stencil to reball this chip (Wylie WL-50, https://www.aliexpress.com/item/4000227755312.html).