I want to run the T-e10s(o) jobs for linux64 and win64 so I went to trychooser and ticked all the appropriate boxes. It gave me this: try: -b o -p linux64,win64 -u none[x64,Windows 8] -t other-e10s[x64,Windows 8] which I dutifully pushed to tryserver. Tryserver didn't run the linux64 talos jobs though. See https://treeherder.mozilla.org/#/jobs?repo=try&revision=9fdb790d9e3f2b2e337309706af66594164d8969

Say hello to the Second Hard Problem. Taskcluster wanted its jobnames to be things like talos-other rather than other, so it invented talos-try-name to hold the "other" name. But it also didn't want to have two actual jobs, "other" and "other-e10s" (and mochitest-1 and mochitest-e10s-1, etc.), so it just has one job with an attribute for e10s that defaults to both unless there's no e10s variant for a job, when it's then false. So two jobs exist in the full taskgraph, talos-other and talos-other-e10s, but they both have the talos-try-name other, and if you ask for -t other you will get both non-e10s and e10s, but if you ask for -t other-e10s, well, there's no such thing in the set of talos-try-names.

Missed including the workaround, while I was busy amusing myself (though you've no doubt long since solved your problem): "-t other[x64],other-e10s[Windows 8]", which only gives you one unwanted non-e10s job on Linux64.

This is either fixed or, now that e10s is just about everywhere, not an issue.