Samsung is a separate kettle of fish in that they make things difficult while keeping the bootloader technically unlocked. Things like a lack of fastboot option, or bespoke for Samsung security changes, and a whole mess of other things. Carriers do also impose addition restrictions for locked models.
Most Motorola phones have unlockable bootloaders. The ones in their range that don’t are the carrier specific models.
Motorola Moto Edge (2021)
Pros: Moto’s classically lite skin with sensible additions that can be turned off if you don’t want them, great battery, great performance, really just a well rounded device.
Cons: I think I legally have to mention the update cadence, and lack of long-term support, but honestly it doesn’t bother me. Android versions haven’t mattered much past, what, Jelly Bean? Though longer security support would be nice. Also, the camera can be a little soft, but I don’t take a ton of photos so I’m rather ambivalent on it.
Honestly, I paid a good price for an unlocked device that still holds up amazingly well. I’m very satisfied.
Coming SoonTM
But yeah, they’re plugging away at it yet. Basically, K-9 sat in maintenance mode for a good while, and while it worked, there’s a lot of tidying up to do yet. I imagine they’ll have the Thunderbird name on it once it has some of the bigger pieces in place.
From what I can tell, Odin should still work on US devices, but I don’t think that its been kept current with devices and Android versions. Most of what I’m seeing is support for Android 9.0 and later, which is pretty out of date at this point. That being said, it’s not something I’ve messed with much, so I’m happy to defer to someone else with more direct experience.