

There is not alternative that is selfhosted to my knowledge. There is PushBullet with a free tier that allows for sending files. You could also use Discord and send messages via their API, and I assume that Matrix has something similar (but I have not looked).
You could also upload them to something else (Paperless or some web/file server) and send a link in your notification. A link can be displayed as a button with actions tag.
I have an X1 Carbon Gen 9 (so a few years old now). I wanted to replace my HDD and they (Lenovo) had videons on how to do it.
I’d say yes. But stick to ThinkPad series. I have an IdeaPad for work and I really which I told my boss to buy a ThinkPad instead. Keyboard has broken twice in 2 years.