I have a folder called "Let's Plays" with sub-folders like so:
- Among Us with Jeremy Dooley
- Factorio with Zisteau - Space Exploration
- Minecraft with GoodTimesWithScar - HermitCraft
- Rimworld with Mr Samuel Streamer - Mushroom Madness
In each of those folders I have folders for each "season" (for long-going series the seasons are by year (Season 2024) but are otherwise "season 1")
Then the videos/thumbnails themselves are like this:
untouchedwagons@storage:/mnt/tank/Media/Videos/Let's Plays/R/Rimworld with Mr Samuel Streamer - Mushroom Madness$ ls *
'Season 1':
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E01 - The Mushroom Apocalypse.jpg'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E01 - The Mushroom Apocalypse.mp4'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E02 - Taking Back the City.jpg'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E02 - Taking Back the City.mp4'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E03 - How Far Would You Go_.jpg'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E03 - How Far Would You Go_.mp4'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E04 - Scientific Breakthrough.jpg'
'Rimworld with Mr Samuel Streamer - Mushroom Madness - S01E04 - Scientific Breakthrough.mp4'
In Jellyfin I have a library for these Let's Plays that are separate from my regular TV Shows.
I use JDownloader 2 to download youtube videos. I normally only download two to three videos a day so doing it all manually isn't that big of an ask, though editing metadata on mkv's is a bit of a pain.