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.