I agree with most of @The Fish's points on Almiron and Kelly, but also on some of @Toonpack's regarding Kelly. For me, we'd have to get a solid amount to get rid of Kelly. Though he did technically come on a free such signings are normally bolstered by higher than normal sign-on fees and wages. Getting the wages off the books might be of benefit if we didn't have an aging centre back population with pending contact expiries. I believe Howe will see Kelly as the replacement for Lascelles as a fourth choice centre back. We know the club are still looking to bring in Botman's longer term partner to replace Schär who is likely to only have another season in him at this level (he's only a few months younger than Paul Dummett). Likewise Dan Burn is of the age where he may only have another year or two in him. Under Howe's stewardship we've seen Lascelles look better than ever and Krafth as well. Kelly has the physical attributes l, so if he has the right attitude (and you assume he does based on us signing him with Howe's history with him) then there's room for improvement as well. If we sell him we'll have to buy someone else. Krafth, Lascelles and Schär's contracts all expire in 6 months time. I expect we'd be looking to extend Schär's but likely not either of the others unless we sell Kelly.
Almiron would go with my blessing. He's always given his all, has a great attitude but has been far from his best when given chances recently. His purple patch was a thing of beauty, and picking up a premier league player of the month award is nothing to sneeze at. The most one legged player I recall playing for us.