Thanks for the PR, appreciated.
Adding a plugin for this site should be fine. But next time, please open a plugin request first, so you don't risk wasting your time should a PR you've worked on be rejected.
Before this can be merged, a couple of things need to be changed, fixed and also cleaned up.
Are you fine with me pushing onto your PR branch with my changes? I had a look at the site and modified your plugin accordingly, and I also added support for VODs. Both live streams and VODs can also be hosted externally, e.g. on YouTube or Twitch, so the plugin should redirect towards that automatically. I also fixed that.
I really don't feel like annotating code in PRs for non-trivial changes that I have already fixed locally, but let me comment on some of the stuff anyway.
$ ./script/test-plugin-urls.py blasttv
:: https://blast.tv
:: 160p, 360p, 480p, 720p, 1080p, 1440p, 2160p, worst, best
:: https://blast.tv/
:: 160p, 360p, 480p, 720p, 1080p, 1440p, 2160p, worst, best
:: https://blast.tv/cs/tournaments/open-2025-season-1/match/24ff9d6c/vitality-mouz
:: 160p, 360p, 480p, 720p, 1080p, 1440p, worst, best
:: https://blast.tv/cs/tournaments/rivals-2025-season-1/match/bfaaa42e/falcons-vitality
:: 160p, 360p, 480p, 720p, 1080p, 1440p, worst, best
:: https://blast.tv/dota/tournaments/blast-slam-iii/match/acabb915/falcons-tundra
:: audio, worst, best, 160p, 360p, 480p, 720p60, 1080p60
:: https://blast.tv/live
:: 160p, 360p, 480p, 720p, 1080p, 1440p, 2160p, worst, best
:: https://blast.tv/live/
:: 160p, 360p, 480p, 720p, 1080p, 1440p, 2160p, worst, best
:: https://blast.tv/live/a
:: 160p, 360p, 480p, 720p, 1080p, 1440p, 2160p, worst, best
:: https://blast.tv/live/americas1
!! No streams found
:: https://blast.tv/live/co-stream
!! No streams found
:: https://blast.tv/live/f
:: worst, best, 144p, 240p, 360p, 480p, 720p, 1080p