Is there an alternate web client for iOS that's only videos from channels you've subscribed to?

Control Panel for YouTube lets you hide Home, Shorts, Related videos, plus anything you don't want to see in Subscriptions (including videos you've already watched), plus you can disable autoplay of random videos, block ads and more, in YouTube itself.

https://soitis.dev/control-panel-for-youtube

You can accomplish this in Firefox with the Unhook extension