Don't really think there'd be much for him. If he likes Isekai he might like high fantasy in general in which case I'd recc Slayers, Sorcerer Stabber Orphen (Which has gotten a recent anime if he doesn't wanna watch the older ones), Bastard!! (Has also gotten a more recent anime)Escaflowne (an Isekai funnily enough), and Those Who Hunt Elves(also an isekai). This is imo a decent mix of both the comedic and serious. If he takes to those I'd recommend the Lodoss OVAs. The TV series is eh but not complete ass or anything but the OVAs are timeless. I'd recc pretty much anything by Mizuno tbh so Lodoss, Rune Soldier and Crystania. Scrapped Princess as a niche pick and Fushigi Yugi as a meme :maybe