For me as a desktop linux poweruser, I find this potential transition pretty intimidating, I've never flashed a phone with a custom rom let alone switch to a completely different OS, and I am not sure if the phone can even be reset to its original OS, if things go south.
Don't worry if you're not ready, just as on the desktop, there are pioneers ahead of you that will clear the way <3
It's relatively easy. It's basically a command for each step you want to do and it tends to fail gracefully nowadays.
If you can install a linux distro you can flash a custom rom on a well-supported phone.
If it were more mainstream I could see GUI apps to manage all this for people, if they don't already exist. Idk I just use adb.
/e/OS at least has a browser based installer[0] for quite some supported phones. I definitely recommend trying it out, installing a custom os on my phone gave me the same feeling when I first ran debian on a laptop struggling under windows (even though the performance gains aren't that apparent in my opinion).
[0]https://e.foundation/installer/