I agree. I was using Pinboard for a long time but with the pricing changes and lack of support, I switched to self-hosting LinkAce (https://www.linkace.org).
> I’d much prefer just being able to use the site on mobile
When's the last time you tried that? Sometime in the past year ish (can't remember exact dates), it got updated to scale properly on narrow screens, and I've had no problem using it on mobile since then.