F(x)tec has been surprisingly communicative over email. They also sent me a replacement display cable after the display swap didn't fix it, and I'm going to try installing that.
Agree to both of that. And waiting 5+ years for that phone has had one nice side effect – it has increased my patience 😉 (Getting a Pro1 and two Pro1 X from other sources in between did help there, of course; on the other hand, I haven't had an actually usable Fxtec phone for quite some time now.)
(lineage-21.0-20241109-nightly-pro1-signed.zip on October 1 security patch installed smoothly (*) using adb sideload and MindTheGapps-14.0.0-arm64-20240925_175633)
And we still can only select one keyboard layout, so no easy layout switching, for multilingual usage.