Obligatory shoutout to [email protected] if you want a more anime-focused discussion. Of what I have watched (or seen enough of to make a judgement) there are a couple standouts. Note that I haven’t really watched much western animation in recent years.

• Frieren: Beyond Journey’s End - [email protected]
• The Apothecary Diaries
• Heavenly Delusion
• Delicious in Dungeon - [email protected] - This one is done by Studio Trigger, so it is a bit stylized, but I adore the animation in this series
• Jujutsu Kaisen - I haven’t watched this, but I have only seen tremendous praise for season 2’s animation (despite the studio’s working conditions)
• Demon Slayer - another show I haven’t watched, but have seen plenty of gorgeous clips

Wildcard answer would be Star Wars Visions. Each episode is done by a different animation studio, so it can be up to personal preference as to which ones you like, but there are some great showcases in the show.

Edit: If you care a lot about animation quality, I would recommend checking out the SakugaBlog. It goes into deep dives on Japanese animation. For example, they did a whole running series on Frieren (link to the first article).

The project relies on extensions that are installed separately to pull content from different services (mangadex, mangaplus, etc.). The other day, the tachiyomi devs removed almost all the extensions that they were hosting/maintaining after a threat of legal action from a Korean webtoon company. Here is a relevant discussion thread.

Here is a guide to a third party extensions repo that was linked in a discussion thread the other day.

I haven’t personally done this with my Tachiyomi yet, but have heard from others it has worked well.