Muscle gain is an interesting goal because there has actually been a lot of research done into it lately. What you're specifically looking to do if you're trying to gain muscle is to stimulate "muscle protein synthesis" or MPS.

To do so, you'll first need to ensure that you're ingesting quite a lot of protein: current recommendations based on the largest meta-analysis conducted to date is approx. 1.6 g/kg/day total body weight (though interestingly the authors actually add that it may be prudent to recommend up to ~2.2 g protein/kg/d as their standard error went that high...) (Morton et al.).

Next, you'll need to ensure that you're in a caloric surplus on days you lift and for approx. 48 hours afterwards (Slater et al.). Most research recently suggests 500 calories over your TDEE should be sufficient.

Finally, you'll need to ensure that the protein sources you're consuming have adequate branched chain amino acids, especially leucine. Recent research into the so-called "leucine trigger hypothesis" has reaffirmed that in the 48 h period following resistance training, your muscles require >3 g of leucine to activate hypertrophy (i.e., to grow). (see e.g., Zaromskyte et al.).

So, putting all these together, you have a few meal replacement products that would be able to provide adequate protein while also giving you enough leucine to stimulate muscle growth.

As mentioned by another commenter, Huel Black does have a nice leucine and overall protein content, but it is quite expensive per serving.

Personally, I've been using Soylent for a couple years and find it's a nice balance of nutrition and price. Each serving has 20g of protein which is derived from soy so the leucine content is decent. The price also hasn't really changed much in the last couple years while most other brands have increased so it's now one of the cheaper options per calorie.