Clean the printing surface with dish soap and tepid water, and adjust your z offset. It appears to be too low from what I can see, but it's hard to tell from a few pictures. It's not supposed to be 0, and will depend on your specific printer, extruder, ... You should aim to have fully filled squares, with no apparent "scars" on the surface left by the hotend moves. A nice rule of thumb is to be able to barely move a sheet of paper between your plate and the hotend freely without feeling friction (make sure to clean the tip of the hotend before). If after these steps it still produces these results, maybe there is an issue with you bed planarity, but most likely your pla has gone bad (I've even seen sealed bags go bad over a few years), try with a freshly dried filament, or a new roll from a reputable source
slock
IIRC zip can, but doesn't by default. Source : wasted 8 hours trying to figure out why something didn't work anymore (had to switch from tar to zip because stupid security system wouldn't let me transfer the tar file)
Random idea that might work: Try to install ReFind from windows, it should work and allow you to boot from random thing more easily. Then try using it to boot from the SD card. Don't forget to turn off secure boot. If that doesn't work, the right idea is indeed to "burn" the media on a partition, however you will also encounter some amount of headache with this option: an installer is not a single partition, but multiple ones. You could try only having the "main" partition on disk, and use refind to boot it too.
TL;DR: ReFind could help you. Turn off secure boot.
Let my add a bit of love for the wurlitzer too :)
Can confirm, in my head op's post meant : "I replaced some old appliance with something quite standard that won't bother me for years". The fizzing is just replaced with the warmth of undisturbed uptime after about 4-5 years
Didn't read this particular article, but using a pi as a router works rather well. I've been using one as my main router for years now, with openwrt. You get a CPU fast enough to handle QoS without issues, more than enough power to run a few additional things if you want to (wireguard, AdBlock, ...). Only thing is : the wifi is trash. Doesn't matter for me (I just use the integrated wifi for a guest network, main network have dedicated APs)