It seems that the Linux Foundation has decided that both “systemd” and “segmentation fault” (lol?) are trademarked by them.
I have rather serious doubts that this is legit. More likely some joker pretending to be from the Linux Foundation sent Redbubble a takedown request.
I agree. Of the 188 marks registered to “The Linux Foundation” with the USPTO, there does not appear to be a mark for “systemd”, “fsck”, or “segmentation fault.” My guess is this is an imposter claim and the artist should counter notice this claim to Redbubble.
FWIW (and assuming the link works) here’s the marks ever registered to the Linux Foundation.