I fiddled some more with ffmpeg, and thanks to piping in #jj (a more recent version of the file-based #ii #IRC #CLI client?) to a #drawtext filter, I now have #Twitch chat overlayed on the stream, sort of.
Not quite satisfied with how it refreshes, but I'm sure I can tweak that.

#Revision2020

https://mastodon.social/media/fpybd2KWeVig4OY6OaE

Hah!
Got the #Revision2020 #demoparty #Twitch livestream playing on my #PS3, with a chat overlay!
Well, somewhat; I need to run it from a bit more powerful hardware than #Termux on my #Xiaomi #MiA1, but #FFMPEG and #streamlink should be easy enough on #Windows...

https://mastodon.social/media/VvoTsy7dWMOjxkeYSXk

Alright, fiddled some more with it, and now got the #Revision2020 stream running a bit more stable on my #PS3 by streaming it from @Siiw's #Windows PC, rather than from my phone.

This way we can more easily have it on in the background, while still using the PC for other stuff. :)

Tools used:
#streamlink
#ffmpeg (with #drawText filter)
#goRtmpServer
#mIRC
#tail
#awk
#UniversalMediaServer (aka #UMS, for the #DLNA support)

https://mastodon.social/media/KwtRCoZZeucNGrHG7F0