Ok, I've just founded a Player.log file in the following configuration directory "/home/XXXXX/.config/unity3d/Duolc7/LaCaja_LaCaja-CosmicJam02_2020" which contains just one line:
"Failed to load il2cpp"
IL2CPP scripting backend has been recently made available for Linux builds as alternative to Mono (for instance Unity Editor 2019.2.x series, the last one I've used so far, would not allow Linux building with such sripting feature). So, consindering I'm using a Lubuntu 18.04 LTS O.S., it's more likely an engine bug with older Ubuntu-like systems or due to a not expected target Linux system when is different from the one on wich you have compiled originally.
As info reference take a look at this Unity forum thread: "https://forum.unity.com/threads/failed-to-load-il2cpp-when-starting-linux-build-on-mint.815664/".
Just for testing you could also try building towards Linux with Mono enabled and upload such version, then I'll tell you if that one works instead.
Anyway, thanks again for your interest!