found 1115851 140.3.1esr-1~deb11u1 thanks I found at least a workaround of some sorts:
alias ff='xdotool sleep 5 search --sync --class firefox windowsize %@ 1025 769 windowmove %@ 0 0 & eatmydata firefox-esr' The five seconds sleep are subject to local experimentation. Unfortunately, it doesn’t work without (that search --sync should make it, but perhaps Firefox starts invisible windows before the main one). The sizing-then-moving makes it use up the whole screen by giving it a size larger than the screen (confirming the fencepost issue). Just in case others stumble on this.
