I'm thinking Snapdragon 8 Gen 2. Other processors are welcome if the phones are unlockable and are ideally somewhat likely to have rom development in the future.
Here's an advice before buying any phone check their xda and telegram groups if development is there. Most commonly devs don't buy overpriced devices cause majority people also avoid them. You'll find more Roms in a 300- 500 dollar device compared to a 1000 dollar one.
I have a ximi phone with around 20 25 custom rom development lots of kernel development. Roms are almost bug free.
What model and what processor?
I would like to buy a phone with a flagship processor from a few years ago for a discount ideally. I have an exynos note 9 atm, and it's fast enough, but the battery is slowly becoming unusable and the screen has hairline cracks.
I'm looking for a flagship Snapdragon phone but the range is so limited with little development that I'm even considering buying an iphone istead and using my note9 for entertainment.
I'm using mi 11x, globally it is known as poco f3. Development is phenomenal roms are almost bug free and good for daily use.
Specs are snapdragon 870 its just a rebranded flagship processor 865. Handles tasks effortlessly, battery life is 6 hours of screen on time on 120hz, you'll get 9-10hours if you use 60hz.
I'm currently running a custom rom based on CLO project. Works fine for me. Idk how the current market it. Previous snapdragon phones sucked a lot 888 888+ 8 gen 1 all these were made by Samsung so they overheat like crazy and thermal throttling is another long paragraph.
If you're interested in any other device I'll suggest either go for 865/ 870 or 8 + gen 1 processor (remember the plus) and above. Current cheapest 8+gen1 will cost you around 400-500 dollars.
It seems like ROM support from lineage-os has slowed down significantly these last two years and are only supporting pixel phones