How to fix an incorrect resolution setting without ADB

I'm running Android TV on Lineage OS, on a Raspberry Pi 4. After changing the resolution setting, the connected display (a TV) no longer displays anything but the message "Video Format not supported". How can I change the resolution setting back/reset it? I have SSH enabled, but I don't know the default user/password for Lineage. USB debugging is disabled - otherwise I would have done this in ADB. I've already done numerous searches on the Internet but can't find anything relevant. Will I just have to reflash and start again? Any help would be greatly appreciated!