I don’t know any MUS options, but I can recommend Mr. D Math. My dd11 is doing a prealgebra readiness this summer and ds14 is doing full algebra 1 this summer. Both love how he teaches and are getting it just fine.
Another option is highschoolmathlive. I’m not sure the materials, but the same lady does singaporemathlive and I use that with ds8.5 and it’s wonderful.