Finally, after numerous trial-and-error attempts, I finally found a phone that works perfectly well with e.foundation #Android - it's Redmi 4X. Very handy size, conveniently placed fingerprint reader and installing /e/ is a breeze, and I get Android 9 on a 2017 phone that runs perfectly well with fully de-googled and debloated OS.
P.S. I've also tried OnePlus 6T but its camera drives me mad, and wanted Redmi 7 Pro but instead got Redmi 8 Pro as the older one is no longer sold, while the newer is not supported by /e/...
Yes, the unlock code is a pain in the ass due to Windows-only app, but otherwise it was instant.