Yes. There is a legit plex app on fire stick and roku. It comes with free live TV and on Demand content, but you can also run your own server on your network with your own downloaded content. If you have an IPTV service you can stream that through plex as well.
Note that Jellyfin is a similar app/server that works the same way and is totally free. Plex is also free, but there are additional features behind the pay wall like GPU decoding, PVR service for IPTV, and others.
It makes you feel so melancholy, doesn’t it? Like a decade ago, I really enjoyed this small YT channel where she did blind playtbroughs of Dark Souls games. She wasn’t much of a gamer in the beginning and started it because her boyfriend thought it would be entertaining having a complete noob try dark souls. He was right. Anyway, she worked her way through all 3 games over the course of about 2 years, but stopped part way into part 3 and never posted again. It’s been like 7 years. I think about it every now and then and check on the channel. I always wonder if she okay.