I hope it’s ok to mention this one here. I was looking for another way to practice grammar besides using Bunpro and stumbled on jpdrills.com.
The site and options are pretty barebones, but it has a ton of vocab/kanji/grammar practice.
The best thing is the explanation for all the grammar lessons. Often very detailed, also explaning while the other multiple choice answers are wrong.
I study Japanese for 2 years now and somehow never saw this site mentioned before. Hopefully it can help others too here who also need more practice like I do.