On Arch you can get this from the aur (package not maintained by me):

mpv-sponsorblock-minimal-git


This is a much more simple version of the sponsorblock mpv plugin.

There are no other functions in this other than the sponsor skipping. Also this 
uses curl rather than python to get the ranges. There is also no cache so the 
ranges may get redownloaded if you watch a video more than once.

b toggles between on/off

Link to the original mpv sponsorblock plugin:
https://github.com/po5/mpv_sponsorblock

Link to sponsorblock:
https://github.com/ajayyy/SponsorBlock