Lineageos is still here, GrapheneOS and CalyxOS is more updated and presumably more secure and private, but Graphene only supports Pixels and Calyx supports Pixels plus some other models. Pixels should be your best bet in terms of ROM compatibility.
It sucks. There's basically no other choice except a Pixel phone. And even some of them are locked if you buy it through your carrier.
I would get some Linux phone even if they aren't perfect, but I have no cell reception, and rely on Wifi calling, which seems to be some proprietary thing that only Apple and Google are able to implement.
Use a Pixel phone running version of GrapheneOS built and signed by you with your own keys, or use stock GrapheneOS and don't lock the bootloader, and add root access if desired.
That's the only hardware/software system that guarantees both total freedom, support for mainstream apps, good security and a quality device.
Donate. Though so far the project is in good financial status.
Since my own finances got to be a bit stricter, I try to donate in packages of $50 ocasionaly as to the project having, from me, an a average of $2 a month.
I'm running Lineage OS on a Moto g100. Overall, I'm really happy with it. I have full control of my phone and it has the hardware features I wanted - headphone jack, micro sd, two-day battery, and a fast enough CPU that it never feels slow.
Motorola has an automated process to get the bootloader unlock code, and the whole process was fairly straightforward.
LineageOS even passes SafetyNet, however there's an additional CTS Profile check that some apps do, and passing that requires rooting the phone, which is turn requires a SafetyNet bypass and makes updates more tricky because LOS updates un-root the phone.
Nobody else (that I saw) mentioned it, but PostmarketOS [0] has a decent number of (community) supported devices, is Free and more than a de-Googled Android distro - it's actually based on Alpine Linux. I've previously run it on my Pinephone Pro, but images are available for multiple Samsung handsets as well [1]
10-15 years ago, when I had a lot more free time, I used to put CyanogenMod on my phones and play around with that.
Are there any good open source mobile OS around these days?