Just my two cents on this topic: I used to use an Android phone with LineageOS (this was before Graphene was a thing), and struggled with similar bugs/issues from time to time.

I got an iPhone and never looked back.

Don't get me wrong, as you suggested here, iPhones are objectively worse in a lot of ways. But mostly, it. Just. Works. And, rather than fight the OS on things like VPN configs, ad blocking, browser usage, etc, I've found that I simply use my phone less, and tether my phone to a real computer more often. Paired with a small chromebook or other laptop running Linux, or (gasp) even MacOS, I just don't use my phone as much as I used to.

On the plus side, iPhones are supported for a long time, have a secure lockdown mode which you can enable if you're extra paranoid, and have "don't need to think about it" full-device encryption including full phone backup support. If your phone ever dies or you want to upgrade, you can load a full backup/image from your old device on to your new one with close to zero fuss (just gotta deal with USB 2.0 speeds on all but the newest phones :)

One final note, you don't need to sign in to an account to use iOS as far as I'm aware. You lose out on the sync/iCloud stuff that Apple provides, but it sounds like you don't care much about that anyway.

Fairphone 5, Shift6mq, Oneplus 11, Xperia Pro 1, Motorola Edge 40 pro. Avoid ios like wildfire. I use an iPad and it is buggy, expensive, and full of spyware, really bad if you want any privacy (and it doesn't have custom rom support at all)

At 8 months old it should be well within warranty. Just get it fixed.

First, don't buy new phones. You're paying a massive premium to be first. Especially since you're going to flash a rom, which has a little risk anyway (I've bricked phones by flashing, though not for years).

I just upgraded from a 2017 flagship to a Pixel 5 (only because my cell company decided to stop it working on their network, when I can throw a different Sim in and it works fine). I was able to buy 3 Pixel 5's for less than you paid for your new phone. Which means I have a daily driver, a hot spare, and a test device for a little over $400.

If my daily breaks, I pickup my spare and swap the SIM, since I keep both phones synced with Syncthing. I don't even have to login to anything because that's all done. (I had 4 functional devices of my 2017 phone, they had become so cheap).

So pick a 1-2 year old model that you like the features, and pay far less for it.

Before (finally) coming to the pixel, I would look at the Lineage device list, then check those phones out at gsmarena.com and phonearena.com to see which I'd prefer, because Lineage has the broadest device support that I've seen.

Today I run DivestOS, a fork of Lineage with some changes to a few things. I forget now exactly what I preferred (I'd have to pull up my comparison spreadsheet), but average battery consumption is a staggering 0.5% per hour, with microg services installed and a couple apps using it. Consumption average increases to about 4% per hour when I'm doing a lot of intensive stuff - copying files over the network, using nav, watching a video, etc.

I just had a purple line appear on my pixel 8, google offered me $490 on trade for a 9. The line is intermittent so I just rated my phone as good condition for the trade in. There is an extended warranty on the problem so if they try and give me any shit about it I'll just reference that. If you do trade it in, make sure to uncheck the box that says you'll accept less on the trade if they decide the condition isn't as described. I have no actual evidence, but given my fairly extensive history dealing with googles customer service I think they may try and screw you over on the trade.

Maybe fairphone is up your alley?

The next best is probably to pick a phone from DivestOS's list of supported devices, and preferably ones with a re-lockable bootloader

Custom roms with relocked bootloader only work on pixels by design. You'll have to live with an unlocked bootloader.

As for easy installs, Murena's e/os exists with support. But I can't vouch for their cloud ecosystem. Other than that, maybe an officially supported lineage device. You will lose safetynet on both unless you want to root.

Fairphone is an option. Can be relocked. It is not important, what Fairphone supports but if it is supported by custom ROM developers. Fairphone is supported by most. But please avoid using Calyx or iode. They are both outclassed by Divest.

At least for /e/OS I can assure that relocking is simple enough. As there is partnership between Fairphone and Murena (/e/ developers) OTA updates are safe for future. Unfortunately the Fairphone support is horrible and /e/ is always too far behind security patch level.

Any supported phone with lineage OS? Primacy is really good but not as much security focused as GOS

https://shop.iode.tech ?