`git bisect --first-parent` is just as easy as a bisect on linear history. (It just follows the "linear" line down merge commits via their first parent, which by convention should be their "base" parent.) Plus it gives you the option to bisect "inside" a branch if you need to inspect something "low level" once you've narrowed down the "branch" based on merge commit. I think if `--first-parent` were the default to git bisect a lot more people would care a lot less about "linear commit history". But it is still an easy flag to apply yourself.