With i3, is it possible to have all new windows open in fullscreen by default? As far as I have been able to find, this is only possible for specified programmes.
You can use the following configuration setting:
for_window [class=".*"] fullscreen enable
for_window [CRITERIA] COMMAND setting runs
COMMAND for each new window matching
CRITERIA. i3 uses PCRE (Perl-compatible regular expressions) for pattern matching, so the pattern
.* matches any number of arbitrary characters. Meaning it matches any possible class name, even empty ones.