@paradadf Thanks so much for your help. Happy I'm not yet abandoned alone 
Actually, I have already tried everything I can. Of course I tried with blueMSX and fMSX with different versions.
One thing I found meanwhile, there is an error when I run a game in verbose mode via ssh:
| [INFO] [MIDI]: Initializing ... |
| ALSA lib seq_hw.c:466:(snd_seq_hw_open) open /dev/snd/seq failed: No such file or directory |
| [ERROR] [MIDI]: snd_seq_open failed with error -2. |
| [ERROR] [MIDI]: Initialization failed (list of input devices unavailable). |
Should this be a reason? This is a vanilla install with fMSX BIOS only. If you want me to try something different for logging, please let me know. Thanks!!