You can disable javascript in qutebrowser, and the default adblocker works pretty good if you remember to update your sources, but I agree that it's not like ublock Origin
uMatrix gives you way more fine-grained control over this (JS on/off per-domain and per-subdomain) along with lots of other features and a great UI that makes all this manageable. Just a simple on/off switch for JS is no comparison.
However, there is this: https://gitlab.com/jgkamat/jmatrix
It's quite a hack and I have no idea where it is UI-wise, but it seems to work for some people at least.