Water-damaged, bootlooping Pixel 2XL can't be detected by PC.

So my 2XL originally got submerged under the pool under a minute a few months ago. It's bootloader-unlocked running a custom ROM.

I had it repaired in one shop and they were able to fix most of it. Problem is it still can't get detected in any PC, even in fastboot mode. I reinstalled the drivers, tried different cables/ports but no luck. I mistakenly did a factory reset and now it just bootloops. For some reason there's no recovery, I can only access the bootloader.

I left it in the drawer after a few months. Another repair shop replaced the charging board but unfortunately it's still not being detected. They suggest I replace the motherboard but it's kind of pricey and there's no guarantee it's the problem. Are there other things I could do aside from that, maybe clean the insides again?