

Works mostly great out of the box, but on a 4K monitor you may wanna use Gamescope to upscale a smaller window.
gamescope -h 1080 -f %command%

Works great aside from crackling audio
Many of the sound effects were crackling. I found a fix here that involves reencoding the game's audio files to work around it: https://www.gog.com/forum/sid_meier_s_alpha_centauri_/fix_for_static_sound
The map is moved by moving the mouse to the edge of the screen, but this doesn't seem to work in a multi-monitor setup. I haven't bothered to try to work around it.
Works great out of the box. Used gamescope to upscale the screen for a 4K monitor.

Crashes after a few minutes
Tried playing the default game and used various communtiy patches, but would reliably get freezes (that required restarting my PC to deal with) after a few minutes of gameplay
Very minor clicking sound associated with some menus

Game looks good but after 5 minutes crashes to desktop.
Modified the .ini files, disabling some flags as suggested. The game throws a segfault 5 minutes into the game, mostly after clicking on a city.

Some numbers might be a tad small, but it's mostly readable.
Minor cackling and repeated input sounds when dealing with some dialogs, but they are rare and go away on their own.
Needed to browse to the save games folder manually every time I wanted to save or load (it's under .steam/SteamApps/common/Sid Meier's Alpha Centauri/saves)
It's one of those games that benefits from a keyboard, but it's playable and as addictive as ever.
Game launched out of the box, but didn't display the mouse cursor. Had to install a community patch and a new renderer. Tried with GE but the game crashed on the first turn. Normal proton works fine though, played a few turn without any obvious issues

gamescope -b -h 1080 -H 2160 -S integer -- $( echo %command% | sed -r "s|proton waitforexitandrun .*|proton waitforexitandrun|") thinker.exe
Mouse cursor won't work unless you disable the opening movie. Change the line DisableOpeningMovie=0
to DisableOpeningMovie=1
in Alpha Centauri.ini
Mouse cursor not present without disabling movies