Honestly, Custom ROMs have been in decline of usage since few years.
There are also Other ROMS like Pixel Experience, PixyOS, Havoc, evolutionX, PixelOS, Paranoid, Derpfest, CrDroid and lot more.
The reason for the drop is due to a combination of reasons like better OEM UI, unpublished Kernel code (Chinese OEMs, Mediatek), locked bootloaders and Safetynet issues.
I'm obstinate as fuck, and I have a downright unhealthy resentment of having software capabilities taken away. As long as there's a single setting or feature that I can get from a custom ROM that I can't get on stock, I will use them.
Many versions ago, Google removed the "hold back button to kill foreground app" functionality, and I'll use LineageOS soley to keep that (but there's plenty of other reasons). The ability to restore useful features that Google and OEMs take away is an absolute necessity for me.
It's almost enjoyable; I get a kick out of telling Google to fuck itself and restoring my device's capabilities.
It's hard to find estimates of android devices, but most reports I found indicate around 3 billion, and this makes us around 0,05%. I expected it to be low, but not like that...
I had LineageOS on my Nexus 4. Every damn phone I've had since hasn't had any custom ROM available (and one couldn't even be rooted; fuck Samsung). I want it back.
I wish I could install lineage on my s10+ snapdragon. I just got this phone and now I just ordered a pixel to get grapheneos. I was willing to pay this guy on telegram to unlock my phone so I could try to get lineage to work or at least a custom rom, but my bootloader is one update off, I have v6 but he only supports up to v5. I hate ordering new devices when my current ones are still functional. I also am getting rid of my fitbit I also just got and replacing it with the amazon band 5 since it can connect to gadgetbridge. Degoogling is expensive, it shouldn't be this bad just to get privacy. I'm not sure what to do with my devices I am replacing, but I hate that they had to be replaced in the first place. I also switched from google services to proton mail/drive/vpn.
And some applications still refuse to launch on it, preferring an outdated version of Android because Google does not send its security updates after 3 years.