Apple riled do-it-yourself upgraders when it launched M1-based Macs with seemingly non-upgradable memory and storage, but there's apparently a way to improve your system— if you're willing to throw caution to the wind. MacRumors has learned that technicians in Guangzhou, China have found a way to detach the RAM and SSD chips to replace them with higher-capacity parts. You could theoretically upgrade to 16GB of RAM if the base 8GB isn't cutting it, for example. MacOS recognizes the upgrades as if it they were official.
As you might imagine, though, the process is fraught with peril. You're removing soldered-on chips and replacing them with components you aren't about to find in a store — this is a difficult procedure guaranteed to void your warranty. You'd also need to track down RAM and SSD chips that are at least as fast as Apple's picks if you want to avoid bogging your Mac down.
This does show that the M1 is more flexible than it appears, though. It also wouldn't be shocking if future Macs (particularly desktops) with newer CPUs offer easier upgrade paths, even if they're still unofficial. Think of this more as a glimpse of what might be coming rather than something you'll want to try right away.