The degooglization is a hard one for me, but hopefully in the near future my Umbrel will replace all their functions. Also looking into getting a Linux cellphone for my next phone. Do you have one? I am concerned it won't be Japan compatible.
Discussion
Yes I use degoogled, custom rom phones for years. It is worth to buy an older one (if you make a brick from it, you can simply throw it to the trashbin 😁). But if ylu have some routine, you could try a most modern phone. But you have to choose carefully. So befire you decide, read through the Lineage webpage (or other custom rom's webpage).
The Linux phones IMHO not soo good (but the Android is a kind of Linux, so I mean the other Linux distributioms for phone).
For Umbrel hardware I wont pay, I have all the software as I wanted. But if you not an IT advanced user or pro, you could use it (most of them unnecessary for an average user)