Hey all, (actual question in bold, sorry I ramble)

Long time Arduino/drone/urmother tinkerer but was out of the game for a couple years due to a mental health issue. I'm starting to get back into things and it's a long story, but as short as I can tell it: depression > emergency trip to hospital = ambo crew didn't think to lock the front door of my place > my place was pillaged in the two months I was stuck in hospitals. So I'm not just catching back up with knowledge but also tools and components (I will forever mourn the loss of my vast and unnecessary collection of eclectic microcontrollers; in particular my Sparkfun Pro Minis with the black PCB). A couple redditors made my journey unbelievably easier after seeing a post I made about the sole tiny parts organizer that survived the purge falling out of a car when parked and dumping the last of my treasures onto the asphalt (which for the record, Satan, was a completely unnecessary extra "fuck you") and sent me a few D1 minis and misc breakout boards/tools. I can't even begin to express my gratitude to those dudes, this community is awesome.

Anyways, I'm already rambling so I'll get to the point: I fortuitously stumbled across an oscilloscope. It definitely wasn't at the top of my list of which order to re-buy things in but hey I finally had some good news for the first time in a long time. It's a Siglent SDS1202X-E which is a huge upgrade over my old analog scope which I'm almost positive was hot considering the price I paid on Craigslist for it and that I kept a Sparkfun oscilloscope analog clock board hooked up to most of the time. I was reading through the documentation and had a quick question:

The scope states that it's a "2 EXT" channel model, and from what I can gather that essentially means I don't have to take up a channel with my trigger, meaning I could actually monitor two channels and still trigger as if I had 3 channels, correct? Can someone correct where I am off in this understanding?

I'm going to blame my brain, life, and long break on my woefully inadequate knowledge on how scopes work instead of admitting that I never took the time to truly learn the ins and outs. Does anyone know of a good place to really learn how to use a scope fully? Let's just pretend I am starting from square one when it comes to scopes, just for fun and totally not because that's true.

My last question is regarding ATMega828Ps (specifically ones with the ADABoot Arduino compatible bootloader on them). Two of these survived the purge and I'm trying to use it on a breadboard. Does anyone see anything wrong with the way I have this set up? I apologize right now for only using red, black, and white wire and not using them correctly. Here's a picture of what I'm working with; I have a 10k pull-up on pin 1, pins 7 and 20 are going to the 5V rails and 8 and 22 are grounded with both pairs having a .1uF cap between them. Pins 9 and 10 have a 16Mhz crystal bridging them, with both legs having a 22pF caps pulling them to ground. As part of the circuit I'm working on pin 4 (Arduino pin 2) has a momentary between it and ground, and pin 18 (Arduino pin 12) just has a jumper that will eventually connect to the data pin on an RGB LED strip. The circuit and code works perfectly fine when inside an Uno, so before I start hunting down potential issues with the chip itself I figured I'd make sure I'm not making some monumentally stupid error in the extremely simple circuit. I'm super big brained and didn't refresh myself on the documentation before just throwing the chip into an Uno and trying to upload my code that way, and after checking the Adafruit website says to select a "DUEMILANOVE with ATMEGA328" as the target in the IDE so I'm hoping I can re-upload the code with an FTDI cable and that I haven't permanently borked this chip.

I'll stop wasting your time now, anyone who treads through my meandering diatribe and takes the time to point me in the right direction I give many, many thanks in advance.