So far I can only think of "The Titan's Bride" and "Kyou Kara Maoh" that are clear-cut bl isekai stories. The titan one is yaoi and the Maoh one is shounenai as a head's up. both have manga and anime adaptions so I recommend them to you!
Omg! I almost forgot "Silver Diamond!" It's a shonenai manga that I really loved when I was younger. It's very long winded and it tackles a lot of philosophical topics so I feel like you kinda need to be mentally prepared for the argument of freewill and stuff like that.
Thank you for the recommendationsヾ(❀╹◡╹)ﾉ~
You can search it at the tag
Just type 'isekai bl'
Can anyone recommend me yaoi isekai like this, it could be novels or manga, pls （/TДT)/