nadenislamarre
It seems that Atari800 emulator starts with model set as Atari 800 rather than Atari 5200. System can be changed to A5200 by pressing F1 (while in emulator) and navigating to change system options, then doing reset of Atari (F8 I believe). The problem is, that while the emulator configuration screen is open ESC key is used to navigate back to the previous menu. Since it is used also to exit emulator, I'm unable to save config file with Atari system selected to 5200 (there must be atari800.cfg file somewhere).
Note on the 5200 roms, I remember converting my games using Altirra (Atari emulator on Windows) to include information on which type of the cartridge game uses (8k or 16k etc). Without this information, Atari800 emulator normally would display screen asking about cartridge type (assuming 5200 model is set in the config file).
With cartridge type saved in the game file header, emulator would start right away. I tried this with Decathlon (didn't have joypad connected, so I used keyboard instead). F4 works as START key.
On the side note, can someone tell me if there's anything wrong with my web browser or Batocera forum. Each time I try open forum topic, I get "Oops! Something went wrong, please reload page and try again." message. I can read whole posts because of this and also posting is very difficult.