Cannot add Personal Access Token in Vivaldi Browser #2129

I'm trying to use Refined GitHub with the Vivaldi browser (Chromium-based). Unfortunately, when I try to paste in my Personal Access Token to be able to use it, nothing happens, and I'm prompted with "Please match the format requested" (even though I'm copypasting my token exactly as generated by GitHub.

Guessing it's not compatible with the Vivaldi Browser?