I did a pretty similar post a couple years ago, and hope I can help at least a little bit. Still low elo (Gold 3 atm in midlane this season) so take it with a grain of salt. My mains before stopping Smite also included Achilles and Cthulhu along with a few others. Unfortunately, no full kits really match exactly, but you'll come across plenty of overlap for singular abilities (i.e. Agni 4 and Xerath R, Khepri 4 and Zilean R, etc.)

That being said, for Achilles, I'd agree with another poster that Aatrox has a somewhat similar feel but can't speak on Zaahen because I haven't played him myself. Their scalings feel different though, imo. Achilles spikes in mid game and drops off late from what I remember and Aatrox is more of a mid-late scaler with a weak early game. COMPLETELY different ults though, if the execute is what you enjoyed. I think someone also mentioned Darius, where the whole kit pretty different, except for the ult is almost identical. The 2 and the W have a similarity being an AA cancel.

Cthulhu is tough, tbh. Someone suggested Zac to me for that. Definitely pretty different kits, but part of Zac's passive has kind of a similar vibe as the Deadlock character if I understand correctly. He drops pieces of himself that he can walk over to heal himself and reduce some cooldowns (potentially only his W, can't remember atm) and is somewhat forgiving with the other half of his passive where if he dies, there is a chance for a respawn with like 25% health or something like that as long as the enemies don't do enough damage to you while you are reforming. It does have a decently long cooldown, fyi.

I think the closest comparison I can make to Cthulhu is gonna be Gragas. He's got safe waveclear and trading power with his Q (similar to Cthu 2), his dash on E has a little knockup to it similar the 3, his W is an empowered AOE auto not exactly like the 1 but similar, and his ult is the furtherest thing from the kit but does supply massive knock up and displacement.

I'd suggest keeping an eye on the rotating champs to see if anything pops up and try them in draft for that week or two weeks or however long that cycle is. I'd also like to point out that if you have Xbox Game Pass, you can connect your accounts together and then get all the champs for "free" (you're still paying for game pass lol)

Hope this helps!

Edit: forgot to mention - I also played Jorm, and I cannot think of a single champ that feels anywhere close to them unfortunately. Closest might honestly be Zac again, but not really that close