RSI
My work from home setup is perhaps different from some.
I've gone with laptop only and like the freedom of moving around the house. With the kiddo in virtual schooling, being able to sit down at the dining room table on a whim is great. As are video calls from the stairs/bedroom/breakfast-nook/patio etc
My body has not reacted with the same enthusiasm.
In the before times, I drove to my office, had a "normal" external monitor/keyboard/trackpad setup. Now I type solely on my MacBook Pro keyboard. It's super convenient to have the laptop on various tabletops or just my own lap.
My arms are telling me another story.
For one other surprise 2020 has brought me is RSI. Specifically Tennis Elbow of all things. The angle of my arms as I type isn't helping. Short term I'm taking anti-inflammatory medicine, icing my elbow, and wearing one of those forearm brace thingers.
Clearly I need to re-assess my posture as I move around the house.
While I'm with you on not using the external monitor so far, I have been limiting the locations where I work to just the kitchen table and, occasionally, a table in the garage if Nathan wants to play outside. This keeps my body used to certain positions. I do use an external keyboard and mouse because I stand my laptop on a custom stand to make it sit higher and because the butterfly keyboard in my MBP sucks balls. The left Shift key doesn't register most of the time. Really bad with passwords.
But soon we're building a desk on which I may go ahead and set up my external monitor and standing desk. That will change things a bit.