Lineageos maintains a list and you can filter for devices with official bootloader unlock https://wiki.lineageos.org/devices/. Buy only these devices to signal to these companies that this matters.
Noteably OnePlus 13 and Pixel 9a, both 2025 phones, can be unlocked.
If someone want something also quite recent and cheaper in this supported list there is also motorola edge+ (2023) with good specs. I got myself refurbished with perfect condition for just 240usd.
Noteably OnePlus 13 and Pixel 9a, both 2025 phones, can be unlocked.