I’ll leave this here, in case other people are interested in running ancient games 
After much trouble getting Quake2 to render fast and correctly on the RK3588, I finally found a combo that works well. See here:
Long story short: I just needed the latest version of Yamagi Quake II and the Vulkan renderer. It was that simple
In case anybody is interested, I just spent 3 solid days playing my favorite 80s and 90s Atari, Amiga and DOS games on the RK3588, in the Hatari, FS-UAE and Dosbox emulators respectively, and it was pretty much flawless. The only problem I encountered was the sound in Another World on Amiga, which goes funky after a few minutes, but I don’t think it’s due to the machine.
I guess this is not news to people who are into retro-gaming, but it’s been a long time since I played those games from my youth (long enough to remember that direct CPU emulation just wasn’t quite feasible at real-time target speed on the last machine I tried it ) and now it’s totally seamless. That “slow” ARM CPU is plenty fast enough to interpret 8088-to-386 code or 68K code many times faster than the original targets. Amazing!
But hey, maybe I’m easily impressed
Still, if you like old games, the Reform doesn’t disappoint.
Retro games are the future.
Tried Warzone 2100 on my classic with RK3588 and it works fine via flatpak. Very easy installation, no fiddling required. Vulkan backend seems to have some issues but OpenGL is running quite smooth with >40fps.
Same for Widelands, also available via flathub.
SuperTuxKart works good on RK3588 with medium settings. Download the ARM64 archive, extract, start run_game.sh
OpenTTD is available via flathub. Works without issues, i have not checked a late game yet.
Same goes for Xonotic, available on flathub and works with medium settings ootb.
I can confirm that warzone2100, widelands, supertuxcart and openttd also work flawlessly on rk3588 when just installing them with apt and not as a flatpack.
I need to do more testing, but I can start up and move around in the GoG version of Torchlight II using minigalaxy. It’s a little choppy in town, but aside from a couple of “program is not responding, should I wait?” type dialogs during startup, seems to be okay. I should go back to trying to get steam to start up (it kept crashing on the A311D)
ETA: The steam client starts up and works just fine on the rk3588, but I’m finding getting some things to work challenging – Stardew Valley is fine, but for some reason I can’t get either the itch.io or the steam versions of A Short Hike to work. I can get the “old” itch.io binary to work with box64, but the shadows don’t render right and makes a weird flashing of the color rendering. The “current” one starts, but after rendering the logos it just stops, with no errors on console, but mono_crash json & mem.blob files.
I just uploaded the latest release of box64 to Debian unstable. If you have rk3588, then you can install the box64-rk3588 package instead of plain box64 which was compiled with some rk3588-specific optimizations. The package has box32 enabled, has the box32 binfmt support enabled and ships a script to install steam. With that version, installing steam is as simple as running:
sudo apt install box64
/usr/share/doc/box64/examples/install_steam.sh
You can then run steam from a terminal but maybe consider running it with PAN_MESA_DEBUG=gl3 set or otherwise some games will complain about missing opengl3 support. Kudos to @minute for pointing me to this setting. Here is the relevant thread on fedi: lucie lukas "minute" hartmann: "ok looks like things have progressed in ARM64 lan…" - Mastodon
