I searched for that error message and found multiple answers for that problem, some of them on the official RPGMaker forums. I don't know your exact circumstances but it seems like you need to update some Ubuntu related things regarding fonts.
Alternatively you can try running the windows version through Wine.
I tried to run the windows version through wine and got a whole lot of NTLM support errors as well as Haswell Valkan support is incomplete messages and while it did start, it's just stuck on the Now Loading screen.
I also tried to find this error message online and found it on various different games and all of them found a solution updating different things, but I've updated everything with no change. I also some other stuff involving the files and unsurprisingly got a worse outcome. But you might've gotten something I haven't since I didn't find this on a lot of RPGMaker forums, so if possible, could you direct me to them?
Thank you
