I think your best bet might still be a pixel (probably a-line), since that would be the path of least resistance for software support and custom rom development/rootability. Another fun option is ASUS with great price/performance and a huge battery (I think it’s fairly repairable too?), but it doesn’t seem there’s a community for custom roms. Here’s the main possibilities and downsides as I see them:
Pixel: a little pricey, not great price/performance, not sure on repairability, weird issues with extra sw features apparently getting worse over time
Samsung: forget about custom roms, again not great price/performance at your price range, repairability okay but not good
Fairphone: bad performance, I don’t believe there’s any water resistance and build quality would be a concern for me, unsure about software support but I’d expect good custom rom community
Sony: not a large user base, so I’d assume there won’t be custom roms. I think Sony hasn’t committed to the same software support as other big names. I’d be worried about availability of replacement parts for repairs
ASUS zenfone: out of your price range. Bad track record for sw support